Convertible nucleoside derivatives

ABSTRACT

The present invention is directed to convertible nucleosides and polymer supported convertible nucleosides for use in S N Ar displacement reactions. The convertible nucleosides can be used to synthesize numerous substituted purine and pyrimidine derivatives. An example of a polymer supported convertible nucleoside of the invention is

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is the U.S. National Phase of, and Applicants claim priority from, International Application Number PCT/US07/21808 filed Oct. 12, 2007, which claims priority from U.S. Provisional Application No. 60/829,168, filed Oct. 12, 2006 and U.S. Provisional Application No. 60/895,761, filed Mar. 20, 2007, all of which are incorporated herein by reference.

This invention was supported by the National Science Foundation, grant number CHE-0314326. The United States government has rights in the invention.

BACKGROUND OF THE INVENTION

Due to the high pharmacological, biological, biochemical, and diagnostic importance of nucleosides, facile methods for their modification is critical. S_(N)Ar displacement chemistry is a means of modifying nucleosides wherein a leaving group from the purine base is displaced by a suitable nucleophile.

Many compounds have resulted from S_(N)Ar displacement chemistry of nucleosides, ranging from adenosine receptor modifiers, anti-viral and anti-cancer agents, to carcinogen-nucleoside conjugates. These compounds have utilities ranging from potential pharmaceutical agents to probes of cellular response such as cancer causation. FIG. 1 shows some examples of modified nucleosides that have been synthesized using S_(N)Ar displacement chemistry.

Among the compounds in FIG. 1, compounds 1 and 2 were shown to be potent and selective adenosine A₁ and A_(2B) receptor agonists. Adenosine receptors are of high importance in cardiac, nervous system functions as well as immune systems. Compound 3 was shown to be active against the malarial parasite Plasmodium falciparum. Carbovir, compound 4, showed promising activity as an anti HIV drug and the carcinogen-nucleoside conjugate has been used to probe DNA damage structure in the search for the underlying cause of carcinogenesis.

S_(N)Ar displacement reactions on nucleosides are an important transformation for the synthesis of new nucleosides with a significant variety of applications. Convertible nucleosides that can be used for such chemistry include 6-halo nucleosides and in some cases arylsulfonyl derivatives of nucleosides.

Structures of typical convertible purine nucleosides are shown in FIG. 2. These compounds could be either in the ribo nucleoside or the deoxyribonucleoside series (leading to new ribo or deoxyribonucleosides). Alternatively, any other entity can be attached to the 9-position of a purine that contains a leaving group at position 6 (leading to substituted purine derivatives).

Among the halo nucleosides shown in FIG. 2, compounds 6 and 7 (R═H) are commercially available. Compound 7 is relatively expensive. Compounds 6 and 7 can be synthesized via known procedures, but the methodology involved is quite difficult. The bromo and iodo nucleosides, which are not commercially available, are easier to prepare than the chloro analogs, however, the syntheses are not simple.

The aryl sulfonate derivatives (compounds 12-15), which are not commercially available, also require relatively non-trivial syntheses. In particular, the aryl sulfonylation reactions of hypoxanthine nucleosides that lead to compounds 12 and 13 are quite complex. For example, in the absence of an amino group at the C-2 position, sulfonylation of the hypoxanthine core produces a significant amount of the N-1 sulfonyl derivative which results in a substantial loss of a costly precursor.

Some other nucleoside derivatives shown in FIG. 3 have been developed as convertible nucleosides. For examples of the syntheses, see Fathi et al., Tetrahedron Lett., 31, 319-322 (1990); Ferentz et al., Nucleosides & Nucleotides, 11, 1749-1763 (1992); Gao et al., J. Org. Chem., 57, 6954-6959 (1992); Zemlicka et al., Nucleosides & Nucleotides, 15, 619-629 (1996); Mechtild et al., J. Chem. Soc., Perkin Trans. 1: Org. Bio-Org. Chem., 1825-1828 (1997); Maruenda et al., J. Org. Chem., 63, 4385-4389 (1998). These compounds are either derived from the types of compounds shown in FIG. 2 or require independent syntheses, none of which are simple and/or readily scalable.

Recently it was shown that triphenylphosphine (PPh₃) in combination with iodine (I₂), N,N-diisopropylethyl amine (DIPEA) and either morpholine, piperidine or imidazole resulted in the conversion of hypoxanthine nucleosides to substituted adenine derivatives. See Lin et al., Org. Lett., 2, 3497-3499 (2000). Among these the imidazobil derivative 20 was found to be a useful convertible nucleoside. Subsequently, compound 21 was synthesized through a procedure similar to that leading to compound 20. The mechanism of this transformation is shown in Reaction Scheme 1. See Janeba et al., Nucleosides Nucleotides & Nucleic Acids, 7, 5877-5880 (2005).

Of key importance in Reaction Scheme 1 was the formation of the phosphonium salt which functioned as a convertible nucleoside, and which was formed in situ. Subsequently, the use of 1H-benzotriazol-1-yloxy-tris(dimethylamino)phosphonium hexafluorophosphate (BOP), a peptide coupling agent, was reported for the activation of hypoxanthine nucleosides (Reaction Scheme 2). See Wan et al., Org. Lett., 7, 5877-5880 (2005).

Convertible nucleosides are typically difficult to synthesize, and their prices are high as a result. Consequently, there is a need for convertible nucleosides that can be synthesized through the use of commercially available materials in an operationally simple and efficient protocol.

Embodiments of the Invention

In one embodiment, the invention related to a molecule having the formula ZOR, wherein:

-   Z represents:

-   R represents:

-   R¹ and R² independently represent CR³ or N; -   R⁴, R⁵, R⁶, R⁷, R⁸, R⁹, R¹⁰, R¹¹, R¹², and R¹³ represent,     independently, N or CQ, with the proviso that no more than three of     R⁴, R⁵, R⁶, R⁷ represents N; -   X represents R¹⁴, —OR¹⁵, SR¹⁵, —N(R¹⁴)₂, R¹⁴C(O)—, nitro, or halo; -   Q and R³, independently of each other, and independently at each     position, represent R¹⁴, —OR¹⁵, —SR¹⁵, —N(R¹⁴)₂, R¹⁴C(O)—, nitro, or     halo; -   Y represents R¹⁴ or a saccharide moiety; -   R¹⁴ independently represents H, an alkyl group, a carbocyclic aryl     group, or a heterocyclic aryl group; -   R¹⁵ independently represents R¹⁴ or a protecting group; -   wherein:

alkyl groups are branched or unbranched and have 1-18 carbon atoms;

alkyl groups are optionally substituted with halo groups;

carbocyclic aryl groups have a total of 6-20 carbon atoms, including carbon atoms of substituents;

heterocyclic aryl groups have a total of 5-20 carbon atoms, including carbon atoms of substituents;

carbocyclic aryl groups and heterocyclic aryl groups are unsubstituted, or optionally substituted at any position with one or more of R¹⁴, —OR¹⁵, —SR¹⁵, —N(R¹⁴)₂, R¹⁴C(O)—, nitro, or halo.

In another embodiment, the invention related to a molecule having the formula Z—O—R-(L)_(n)-Po, wherein:

-   Z represents:

-   R represents:

R¹ and R² independently represent CR³ or N;

R⁴, R⁵, R⁶, R⁷, R⁸, R⁹, R¹⁰, R¹¹, R¹², and R¹³ represent, independently, N or CQ, with the proviso that no more than three of R⁴, R⁵, R⁶, R⁷ represents N;

X represents R¹⁴, —OR¹⁵, —SR¹⁵, —N(R¹⁴)₂, R¹⁴C(O)—, nitro, or halo;

Q and R³, independently of each other, and independently at each position, represent R¹⁴, —OR¹⁵, —SR¹⁵, —N(R¹⁴)₂, R¹⁴C(O)—, nitro, or halo;

Y represents R¹⁴ or a saccharide moiety;

R¹⁴ independently represents H, an alkyl group, a carbocyclic aryl group, or a heterocyclic aryl group;

R¹⁵ independently represents R¹⁴ or a protecting group

wherein:

-   -   alkyl groups are branched or unbranched and have 1-18 carbon         atoms;     -   alkyl groups are optionally substituted with halo groups;     -   carbocyclic aryl groups have a total of 6-20 carbon atoms,         including carbon atoms of substituents;     -   heterocyclic aryl groups have a total of 5-20 carbon atoms,         including carbon atoms of substituents;     -   carbocyclic aryl groups and heterocyclic aryl groups are         unsubstituted, or optionally substituted at any position with         one or more of R¹⁴, —OR¹⁵, —SR¹⁵, —N(R¹⁴)₂, R¹⁴C(O)—, nitro, or         halo;

-   L represents any chain of up to 20 atoms selected from carbon,     nitrogen, oxygen, or sulfur

wherein:

the carbon atom is —CH₂—, —C(O)—, or phenyl;

the nitrogen atom is —N(R¹⁴)—,

the oxygen atom is —O—,

the sulfur atom is —S(O₂)—;

-   n is 0 or 1; and -   Po represents an organic polymer, an inorganic polymer, or     combinations thereof.

In yet another embodiment, the invention related to a molecule having the formula ZOR, wherein:

-   Z represents:

-   R represents:

-   R¹ and R² independently represent CR³ or N; -   R⁴, R⁵, R⁶, R⁷, R⁸, R⁹, R¹⁰, R¹¹, R¹², and R¹³ represent,     independently, N or CQ, with the proviso that no more than three of     R⁴, R⁵, R⁶, R⁷ represents N; -   X represents R¹⁴, —OR¹⁵, SR¹⁵, —N(R¹⁴)₂, R¹⁴C(O)—, nitro, or halo; -   Q and R³, independently of each other, and independently at each     position, represent R¹⁴, —OR¹⁵, —SR¹⁵, —N(R¹⁴)₂, R¹⁴C(O)—, nitro, or     halo; -   Y represents a saccharide moiety having the following structure:

-   R¹⁴ independently represents H, an alkyl group, a carbocyclic aryl     group, or a heterocyclic aryl group; -   R¹⁵ independently represents R¹⁴ or a protecting group;

-   R¹⁷ is hydrogen; and -   R¹⁸ is hydrogen or a protecting group; -   wherein:

alkyl groups are branched or unbranched and have 1-18 carbon atoms;

alkyl groups are optionally substituted with halo groups;

carbocyclic aryl groups have a total of 6-20 carbon atoms, including carbon atoms of substituents;

heterocyclic aryl groups have a total of 5-20 carbon atoms, including carbon atoms of substituents;

carbocyclic aryl groups and heterocyclic aryl groups are unsubstituted, or optionally substituted at any position with one or more of R¹⁴, —OR¹⁵, —SR¹⁵, —N(R¹⁴)₂, R¹⁴C(O)—, nitro, or halo.

ABBREVIATIONS

Abbreviations used throughout the specification are defined as follows:

BOP, 1H-benzotriazol-1-yloxy-tris(dimethylamino)phosphonium hexafluorophosphate

BOPNuc, BOP nucleoside derivatives

BroP, Bromo-tris-(dimethylamino)phosphonium hexafluorophosphate

DIPEA, N,N-diisopropylethylamine

DME, 1,2-dimethoxyethane

DMF, N,N-dimethylformamide

DMT, 4,4′-dimethoxytrityl

HMPT, hexamethylphosphorus triamide

HOBT, anhydrous 1-hydroxybenzotriazole

MMT, monomethoxytrityl

PS-HOBT, 1-hydroxybenzotriazole-6-sulfonamidomethyl polystyrene

PyBroP, bromo-tris-pyrrolidinophosphonium hexafluorophosphate

TBDMS, tert-butyldimethylsilyl

THF, tetrahydrofuran

DETAILED DESCRIPTION OF THE INVENTION

The invention relates to convertible nucleosides for use in S_(N)Ar displacement reactions. The nucleosides can be used to synthesize numerous substituted purine and pyrimidine derivatives.

The molecules have the formula ZOR. In this formula, Z represents:

When Z is Z^(a), R¹ and R² independently represent CR³ or N. For example, R¹ represents CR³ and R² represents N; R¹ represents N and R² represents CR³; R¹ represents N and R² represents N; and R¹ represents CR³ and R² represents CR³. In a preferred embodiment, R¹ represents CR³ and R² represents N. R³ is as described below.

In the above formulas, X represents R¹⁴, —OR¹⁵, SR¹⁵, —N(R¹⁴)₂, R¹⁴C(O)—, nitro, or halo. Y represents R¹⁴ or a saccharide moiety. R¹⁴, R¹⁵, and a saccharide moiety are as described below.

In the formula ZOR, R represents:

In this specification, unless otherwise defined, the following definitions apply. R⁴, R⁵, R⁶, R⁷, R⁸, R⁹, R¹⁰, R¹¹, R¹², and R¹³ represent, independently, N or CQ.

When R is R^(a), no more than three of R⁴, R⁵, R⁶, and R⁷ represent N. For example, R⁴, R⁵, R⁶, and R⁷ may represent CQ. In a preferred embodiment, R⁵ represents N and R⁴, R⁶, and R⁷ represent CQ.

R preferably represents R^(b). In one embodiment, R⁸ and R⁹ represent N. In another embodiment, R⁸, R⁹, and R¹³ represent N.

Preferably, when R represents R^(b), no more than one of R¹⁰, R¹¹, R¹², and R¹³ represent N. For example, R¹⁰, R¹¹ and R¹² may represent CQ and R¹³ may represent N; or R¹⁰, R¹¹, R¹², and R¹³ may represent CQ. In a particularly preferred embodiment, R represents R^(b), R⁸ and R⁹ represent N, and R¹⁰, R¹¹, R¹², and R¹³ represent CQ.

Q and R³, independently of each other, and independently at each position, represent R¹⁴, —OR¹⁵, —SR¹⁵, —N(R¹⁴)₂, R¹⁴C(O)—, nitro, or halo. In this specification, halo includes, fluoro, chloro, bromo, or iodo.

R¹⁴ independently represents H, alkyl groups, carbocyclic aryl groups, or heterocyclic aryl groups. In a preferred embodiment, R¹⁴ represents H.

R¹⁵ independently represents R¹⁴ or a protecting group. Protecting groups are as described below. In a preferred embodiment, R¹⁵ represents an alkyl group.

In this specification, alkyl groups are branched or unbranched, and have a minimum of one, two, or three carbon atoms. The maximum number of carbon atoms is eighteen, sixteen, or twelve.

Some examples of suitable straight-chained alkyl groups include methyl, ethyl, n-propyl, n-butyl, n-pentyl, n-hexyl groups and dodecyl and hexadecyl. Preferred straight chain alkyl groups include methyl and ethyl.

Some examples of suitable branched alkyl groups include iso-propyl, iso-butyl, sec-butyl, t-butyl, 1-methylbutyl, 2-methylbutyl, 3-methylbutyl (isopentyl), 1,1-dimethylpropyl, 1,2-dimethylpropyl, 2,2-dimethylpropyl(neopentyl), 1-methylpentyl, 2-methylpentyl, 3-methylpentyl, 4-methylpentyl groups, and 2-methyl, 5-ethyldecyl. Preferred branched alkyl groups include isopropyl and t-butyl.

The alkyl groups are optionally substituted with halo groups. Some examples of suitable haloalkyl groups include trifluoromethyl, 2,2,2-trichloroethyl, 2-bromoethyl, 2-chloropropyl, and 3-bromopropyl.

Carbocyclic aryl groups can be unfused or fused. A preferred unfused carbocyclic aryl group is phenyl. Some examples of other fused carbocyclic aryl groups include naphthyl, phenanthryl, anthracenyl, triphenylenyl, chrysenyl, and pyrenyl.

Heterocyclic aryl groups contain one or more ring heteroatoms, e.g., nitrogen, oxygen, or sulfur atoms, and may be unfused or fused. Some examples of unfused heterocyclic aryl groups include thiophenyl, furyl, pyrrolyl, pyrazolyl, imidazolyl, oxazolyl, thiazolyl, pyridinyl, pyridazinyl, pyrimidinyl, and pyrazinyl. Some examples of fused heterocyclic aryl groups include purinyl, 1,4-diazanaphthalenyl, indolyl, benzimidazolyl, 4,5-diazaphenanthrenyl, and benzoxazolyl.

Carbocyclic and heterocyclic aryl groups may be, unsubstituted, or are optionally substituted at any position with one or more substituents. Some examples of aryl substituents include R¹⁴, —OR¹⁵, —SR¹⁵, —N(R¹⁴)₂, R¹⁴C(O)—, nitro, or halo.

Carbocyclic aryl groups contain a minimum of six carbon atoms. The maximum number of carbon atoms is twenty, including carbon atoms, if any, of optional substituents and/or fused rings.

Heterocyclic aryl groups contain a minimum of five carbons. The maximum number of carbon atoms is twenty carbon atoms, including carbon atoms, if any, of optional substituents and/or fused rings.

Saccharides which can be used in this invention can be any monosaccharide or polysaccharide. Preferred polysaccharides include disaccharides and trisaccharides. The maximum number of saccharides in a polysaccharide is typically ten, preferably five. The saccharides can be in either the D or L configuration. Monosaccharides can be either aldoses or ketoses. The number of carbons of the saccharide can be from three carbons to about six carbons. An example of a three carbon sugar is glyceraldehyde. Examples of four carbon sugars include erythrose and threose. Examples of five carbon sugars include ribose, arabinose, xylose and lyxose. Examples of six carbon sugars include allose, altrose, glucose, mannose, gulose, idose, galactose and talose. Saccharides further include the corresponding 2′-deoxy derivatives.

In a particular embodiment of the invention, Y is a ribose or 2′-deoxyribose moiety, preferably having the following structure:

wherein R¹⁶ represents H or a protecting group; R¹⁷ represents H or OR¹⁶; and R¹⁸ represents R¹⁵. Preferably, R¹⁸ represents R¹⁶ or an alkyl group. The alkyl group is preferably methyl or ethyl.

In this specification, protecting groups can be essentially any group suitable for the protection of a hydroxyl group, as known in the art. The phrase “protecting group” indicates any functionality that is used to replace a hydrogen atom on an alcohol, and which can easily be removed with restoration of the hydrogen without altering the structure of the remainder of the molecule.

Protecting groups are reviewed in Protecting groups by Kocienski, Philip J. Stuttgart, New York, Georg Thieme, 2005; and in Protective groups in organic synthesis by Greene, Theodora W. and Wuts, Peter G. M. New York, Wiley, 1999. Some examples are given below, but are not meant to be inclusive.

A class of useful protecting groups for compounds of the invention is the acetal/ketal class. This class of protecting groups can be represented according to the formula: —C(OR¹⁹)(R²⁰)(R²¹).

R¹⁹ is preferably an alkyl group, R²⁰ is preferably an alkyl group, an aryl group, or a hydrogen atom, and R²¹ is preferably an alkyl group or a hydrogen atom. The alkyl groups of R¹⁹, R²⁰, and R²¹ may be any of those described above, and preferably have one to four carbon atoms, typically methyl or ethyl. The alkyl groups of R¹⁹ and R²⁰ may also be joined to form a five or six member saturated ring. The aryl group of R²⁰ may be any carbocyclic or heterocyclic aryl group described above, and is preferably phenyl, pyridinyl, pyrrolyl, or furanyl. Some preferred acetal/ketal protecting groups include methoxymethyl, ethoxymethyl, tetrahydropyranyl, and benzyloxymethyl.

Another example of a class of suitable protecting groups for R¹⁵ includes the class of silyl protecting groups. The class of silyl protecting groups can be represented according to the formula: —Si(O_(x)R²²)(O_(y)R²³)(O_(z)R²⁴).

In the formula above for silyl protecting groups, R²², R²³, and R²⁴ each independently represents any of the alkyl groups or carbocyclic or heterocyclic aryl groups described above. The subscripts x, y, and z independently represent 0 or 1. When x, y, or z is 0, then the oxygen atom to which the subscript is associated is absent. When x, y, or z is 1, then the oxygen atom to which the subscript is associated, is present.

Some examples of silyl protecting groups wherein x, y, and z are all 0, include triethylsilyl, tri-(n-propyl)silyl, triisopropylsilyl, tri-(n-butyl)silyl, triisobutylsilyl, t-butyldimethylsilyl, t-butyldiphenylsilyl, phenyldimethylsilyl, methyldiphenylsilyl, and triphenylsilyl. Some examples of silyl protecting groups wherein at least one of x, y, and z is 1, include trimethoxysilyl, dimethoxymethylsilyl, methoxydimethylsilyl, trifluoromethoxymethylsilyl, ethoxydimethylsilyl, methoxydiethylsilyl, isopropoxydimethylsilyl, phenoxydimethylsilyl, phenoxydiethylsilyl, methyldiphenoxysilyl, [2,4,6-tri-(t-butyl)phenoxy]dimethylsilyl, t-butoxydimethylsilyl, t-butoxydiphenylsilyl, t-butylmethoxyphenylsilyl, and methoxydiphenylsilyl.

Another example of a class of suitable protecting groups includes arylmethyl protecting groups, which protect a hydroxyl group by converting it to an arylmethyl ether. The aryl group may be any of the carbocyclic or heterocyclic aryl groups described above. Some examples of preferred aryl groups include phenyl, pyridinyl, pyrrolyl, or furanyl, optionally substituted with methoxy, ethoxy, nitro, or halo (F, Cl, Br, or I). Some preferred members of this class of protecting groups include benzyl, p-methoxybenzyl, and p-ethoxybenzyl.

Trityl ethers are another class of suitable protecting group. Some examples of trityl ethers include monomethoxy trityl ether, dimethoxytrityl ether, and trimethoxy trityl ether.

In a preferred embodiment of the invention, Z represents:

-   R represents:

-   R¹ represents CR³ and R³ represents H; R², R⁸, and R⁹ represent N;     R¹⁰, R¹¹, R¹², and R¹³ represent CQ; Q and X represent R¹⁴ and R¹⁴     represents H; -   Y represents a saccharide moiety, with the following structure:

wherein R¹⁶ represents H or a protecting group; R¹⁷ represents H or OR¹⁶; and R¹⁸ represents R¹⁶ or an alkyl group. The alkyl group is preferably methyl or ethyl.

In another embodiment, the chemistry described herein can be adapted wherein convertible nucleoside derivatives are assembled onto a polymer support. These polymer supported derivatives can be used in diversity-oriented and high-throughput syntheses such as combinatorial libraries and for parallel array reactions. Both methods are aimed at the rapid production of large numbers of small molecules predominantly for pharmacological screening. Polymer supported derivatives have found significant use in multi-step organic synthesis as well.

Accordingly, in an additional embodiment, the invention relates to polymer-supported convertible nucleoside derivatives of the formula Z—O—R-(L)_(n)-Po. Z and R are as described above.

Po represents an organic polymer, an inorganic polymer, or a combination thereof Examples of organic polymers include polyethylene glycol, polystyrene, and amino resins. In a preferred embodiment, the organic polymer is a polystyrene such as 1% cross-linked polystyrene-co-divinylbenzene. Inorganic polymers include glass beads, silica gel, alumina, controlled pore glass, and amino-modified controlled pore glass.

Organic polymers and inorganic polymers may be combined to form a composite where an inorganic support is linked to an organic polymer. For example, polyethylene glycol may be linked to glass beads.

Po can be attached to Rat either R⁴, R⁵, R⁶, R⁷, R⁸, R⁹, R¹⁰, R¹¹, R¹², R¹³. The polymer can be attached directly to R or to R through a linker, L.

The letter n represents 0 or 1.

Linker, L, is any chain of up to twenty atoms selected from carbon, nitrogen, oxygen, or sulfur. The carbon atom is in the form of —CH₂—, —C(O)—, or positions 1-4 of a phenyl group. The nitrogen atom is in the form of —N(R¹⁴)—. The oxygen atom is in the form of —O—. The sulfur atom is in the form of —S(O₂)—.

For example, the linker, L, may be represented by -(A¹)_(a)-(A²)_(b)-(A³)_(c)-(Ph)_(k). Each of A¹, A², and A³ is different from the others, and independently represents —CH₂—, —C(O)—, —O—, —N(R¹⁴)—, or —S(O₂)—. Ph represents phenyl. The letters a, b, and c are independently 0, 1, or 2. The letter k represents 0 or 1. R¹⁴ is as described above.

Preferably, at least one of a, b, and c is not 0. For example, if a and b are 0, then c is not 0.

For example:

-   -   when A¹ represents —S(O₂)—; A² represents —N(R¹⁴)—; A³         represents —CH₂—; a, b, c, k, and n are 1; and R¹⁴ is H, the         resulting structure for -(L)_(n)-Po is

-   -   when A¹ represents —C(O)—; A² represents —N(R¹⁴)—; A³ represents         —CH₂—; a, b, c, k, and n are 1; and R¹⁴ is H, the resulting         structure for -(L)_(n)-Po is

In another embodiment, L is represented by -(A¹-A²)_(m1)-(CH₂)_(m2)-(Ph)_(k)-. Each A¹ and A² is different from the other, and independently represents —C(O)—, —O—, —N(R¹⁴)—, or —S(O₂)—. Ph represents phenyl. The letters m1 and k are independently 0 or 1 and m2 is 0, 1, or 2. R¹⁴ is as described above.

Preferably, at least one of m1 and m2 is not 0. For example, if ml is 0 then m2 is not 0.

Synthesis of Convertible Nucleoside Derivatives

Nucleosides may be converted to the convertible derivatives of the invention by treatment with a suitable phosphonium ion and a sterically hindered amine. Suitable phosphonium ions include R^(b)—O—P⁺T₃.A⁻, where T is N(lower alkyl)₂, phenyl, substituted phenyl, or the alkyl groups join to form a heterocyclic ring. Examples of such heterocyclic rings include pyrrolidine, piperidine, and morpholine. Lower alkyl groups are C₁-C₄. A⁻ is a counterion such as PF₆ or halide (F, Cl⁻, Br⁻, or I⁻). R^(b) is as described above. Sterically hindered amines include tertiary amines such as DIPEA, triethylamine, 1-methylmorpholine, and 1-methylpiperidine. These reactions may be carried out at room temperature for about 23 hours to about 68 hours. Some examples are illustrated in Reaction Scheme 3 and in the examples section.

For example, any hypoxanthine core can be converted to a BOPNuc analog so long as other functionalities that would react with BOP are absent. For example, the synthesis of BOPNuc derivatives is shown below in Reaction Scheme 3. The ribonucleoside precursor, BOP, DIPEA and THF were combined in a flask, then stirred at room temperature for 23 hours. The mixture was evaporated, washed with water, dried, concentrated, and purified via column chromatography to yield the corresponding ribonucleoside analog.

For example, the ribonucleoside analog BOPNuc 27 was synthesized from the nucleoside precursor 23 (80% yield). Likewise, the hydroxyl unprotected deoxynucleoside 24 and the ribonucleoside 25 were readily converted to the BOPNuc 28 and 29 (in DMF as solvent), suggesting that no competing reaction occurs at the hydroxyl groups.

Alternatively, nucleosides may be converted to the convertible derivatives of the invention as seen in Reaction Scheme 4 above (or a related scheme with different, but analogous reactants.) First, a phosphine P-T₃, where T₃ is as described above, is reacted with a halogen. The halogen, Q₂, may be F₂, Cl₂, Br₂, or I₂. Preferably, Q₂ represents I₂. In a preferred embodiment, the phosphine is triphenylphospine.

The resulting phosphonium salt, Q-P⁺T₃.Q⁻ is reacted with a nucleoside precursor (Z^(a)O), e.g. compounds 22 or 23, in the presence of an organic base in an organic solvent. Suitable organic bases include DIPEA, triethylamine, and tributylamine. Examples of organic solvents include CH₂Cl₂, DMF, THF, and 1,2-dichloroethane. Displacement by R^(b)—OH (or R^(a)—OH), where R^(a) and R^(b) are as described above, in the presence of an organic base results in the desired convertible nucleoside derivatives. The synthesis is shown in Reaction Scheme 4 below.

Preferred conditions for conversion of compounds 22 and 23 to 26 and 27, respectively, involved a reaction between 1 molar equivalent of 22 or 23 with 3 molar equivalents of triphenylphosphine (PPh₃), 3 molar equivalents of I₂, 8 molar equivalents of diisopropylethyl amine (DIPEA) and 1.5 molar equivalents of HOBT in dichloromethane solvent. The products, compounds 26 and 27, were obtained in yields of 90-96% after purification.

Conversion of Nucleoside Derivatives

The convertible nucleoside derivatives of the invention can be converted to useful nucleoside derivatives by means of S_(N)Ar displacement reactions, as is known in the art. In order to demonstrate the versatility of BOPNuc compounds as convertible nucleosides, a series of solution-phase experiments were performed wherein BOPNuc derivatives 26 and 27 were subjected to a nucleophilic displacement with a variety of nitrogen (primary and secondary amines), oxygen (alcohol and phenol) and sulfur (thiol) nucleophiles. These are schematically represented in Reaction Scheme 5. The results are compiled in Table 1.

TABLE 1 Results of displacement reactions with convertible nucleoside derivatives 26 and 27. Entry BOPNuc Nucleophile Conditions Product yield  1 26 CH₃OH CH₃OH, Cs₂CO₃, rt, 1 h 77%  2 26 CH₃CH₂OH CH₃CH₂OH, Cs₂CO₃, rt, 1 h 95%  3 26 (CH₃)₂CHOH (CH₃)₂CHOH, Cs₂CO₃, rt, 10 h 84%  4 27 (CH₃)₂CHOH (CH₃)₂CHOH, Cs₂CO₃, rt, 24 h, 70% then 82° C., 3 h  5 26 CH₂═CHCH₂OH CH₂═CHCH₂OH, Cs₂CO₃, rt, 2 h 89%  6 26

PhMe, Cs₂CO₃, 105° C., 2 h 86%  7 26

PhMe, Cs₂CO₃, 105° C., 20 h DME, Cs₂CO₃, 85° C., 2 h 75% 78%  8 27

DME, Cs₂CO₃, 85° C., 1 h 81%  9 26

DME, Cs₂CO₃, 85° C., 2 h 82% 10 26

DME, Cs₂CO₃, 85° C., 2 h 81% 11 26

DME, Cs₂CO₃, 85° C., 1 h 87% 12 26

DME, Cs₂CO₃, 85° C., 1 h 79% 13 27

DME, Cs₂CO₃, 85° C., 1 h 72% 14 26

DME, Cs₂CO₃, 85° C., 3 h 68%^(a) 15 26

DME, Cs₂CO₃, 85° C., 1 h 64%^(b) 16 26

DME, Cs₂CO₃, rt, 1 h DME, rt, l h 78% 52% 17 27

DME, Cs₂CO₃, rt, 1 h DME, rt, 1 h 85% 90% 18 28

DME, Cs₂CO₃, rt, 1 h 52% 19 29

DME, Cs₂CO₃, rt, 1 h 58% 20 26

DME, Cs₂CO₃, rt, 6 h DME, rt, 8 h 84% 75% 21 27

DME, Cs₂CO₃, rt, 7 h DME, rt, 9 h 87% 83% 22 26

DME, Cs₂CO₃, 85° C., 4 h 60% 23 26

DME, Cs₂CO₃, rt, 1 h 85% 24 27

DME, Cs₂CO₃, rt, 1 h 93% 25 26

PhMe, K₃PO₄, 105° C., 3 h DME, Cs₂CO₃, 85° C., 1 h 92%^(c) 60%^(c) ^(a)Product is a dimer where both phenolic hydroxyls undergo etherification. ^(b)It is plausible that some epimerization could have occurred at the chiral center since the starting amino acid does undergo partial racemization under the reaction conditions. However, the ¹H NMR spectrum of the product does not show any resolved signals for the diastereomers. ^(c)The N-1 of the nucleophile is attached to the C-6 of the substrate.

Other nucleophiles, such as azide, cyanide, selenides and carbanions (sp³, sp², sp), etc., can also be effectively utilized as nucleophiles in S_(N)Ar reactions with convertible nucleoside derivatives. These nucleophiles result in intermediates that can be used for novel applications and for discovery of new compounds with biological, biochemical and pharmacological importance. Some examples are shown in Scheme 6.

In addition to hypoxanthine cores, pyrimidine cores can also form convertible pyrimidine derivatives by, for example, reacting with BOP. In Reaction Scheme 7, the pyrimidine core, BOP, and NaH in dry THF are stirred at room temperature for 23 hours. The mixture is evaporated, washed with water, dried, concentrated, and purified via column chromatography to yield a convertible pyrimidine derivative.

Synthesis of Polymer-Supported Convertible Nucleoside Derivatives

Any of the nucleoside precursors mentioned above can be attached to a suitable polymer by methods known in the art. In a preferred embodiment, the polymer support is polystyrene, for example, 1% cross-linked polystyrene-co-divinylbenzene with a HOBT loading of 1.02 mmol/g of polymer.

The precursor can be coupled to the polymer by using a suitable coupling agent or by using the combination of hexamethylphosphorus triamide (HMPT: P(NMe₂)₃) and iodine. Suitable coupling agents include BroP and PyBroP as defined in the abbreviations section above.

The reaction is conducted in a suitable solvent. Some examples of suitable solvents include CH₂Cl₂, ClCH₂CH₂Cl, and THF.

Isolation of the polymer and washing with a series of solvents yields the appropriate polymer-supported nucleosides. The polymer loading is in the range of 0.24-0.33 mmol/g.

Using the above procedure, compounds 22 and 23 were converted to polystyrene-supported O⁶-(benzotriazol-1-yl)-3′,5′-bis-O-(tert-butyldimethylsilyl)-2′-deoxyinosine (30) and polystyrene-supported O⁶-(benzotriazol-1-yl)-2′,3′,5′-tris-O-(tert-butyldimethylsilyl)inosine (31) by coupling compounds 22 and 23 to 1-hydroxybenzotriazole-6-sulfonamidomethyl polystyrene (PS-HOBT).

TABLE 2 Results of displacement reactions with convertible nucleoside derivates 22 and 23 and PS-HOBT. Entry Polymer loading conditions (a, b) and cleavage (c) conditions Product and yield^(a) 1 a) BroP (5.0 molar eq), Et₃N (5.0 molar eq), Pol-HOBT (1.0 molar 11% eq), CH₃CN, rt (20 h) b) 22 (2.0 molar eq), DIPEA (1.5 molar eq), THF, rt (65 h) c) morpholine (1.7 molar eq), Cs₂CO₃ (1.7 molar eq), DME, rt (4 h)^(a) 2 a) 22 (1.5 molar eq), BroP (1.0 molar eq), DIPEA (4.0 molar eq), 23% CH₂Cl₂, rt (5 h) b) Pol-HOBT (1.5 molar eq), rt (25 h) c) morpholine (3.5 molar eq), Cs₂CO₃ (3.5 molar eq), DME, rt (4 h)^(a) 3 a) 22 (1.0 molar eq), BroP (1.1 molar eq), DIPEA (4.0 molar eq), 58% CH₂Cl₂, rt (7 h) b) Pol-HOBT (1.5 molar eq), rt (24 h) and then 40° C. (30 h) c) morpholine (2.8 molar eq), Cs₂CO₃ (2.0 molar eq), DME, rt (20 h)^(a) 4 a) 22 (1.0 molar eq), BroP (1.1 molar eq), DIPEA (4.0 molar eq), 65%^(b) THF, rt (7 h) b) Pol-HOBT (1.5 molar eq), rt (17 h) and then 40° C. (30 h) c) morpholine (2.8 molar eq), Cs₂CO₃ (2.0 molar eq), DME, rt (20 h)^(a) 5 a) 22 (1.0 molar eq), PyBroP (1.1 molar eq), DIPEA (4.0 molar Not determined^(c) eq), CH₂Cl₂, rt (17 h) 6 a) PPh₃ (3.0 molar eq), I₂ (3.0 molar eq), CH₂Cl₂, rt (30 min) and  8% then 22 (1.0 molar eq), DIPEA (8.0 molar eq), rt (19 h) b) Pol-HOBT (1.5 molar eq), rt (72 h) and then reflux (4 h) c) morpholine (3.8 molar eq), DME, rt (23 h)^(a) 7 a) HMPT (1.5 molar eq), I₂ (1.5 molar eq), CH₂Cl₂, rt (10 min) and 55% then 22 (1.0 molar eq), DIPEA (4.0 molar eq), rt (2 h) b) Pol-HOBT (1.5 molar eq), rt (22 h) c) morpholine (2.0 molar eq), Cs₂CO₃ (2.0 molar eq), DME (1.0 mL), rt (20 h)^(a) 8 a) HMPT (1.5 molar eq), I₂ (1.5 molar eq), CH₂Cl₂, rt (10 min) and 58% then 23 (1.0 molar eq), DIPEA (4.0 molar eq), rt (1 h) b) Pol-HOBT (1.5 molar eq), rt (22 h) c) morpholine (2.0 molar eq), Cs₂CO₃ (2.0 molar eq), DME, rt (22 h)^(a) ^(a)This step was performed to cleave the nucleoside from the polymer support. The yield of the resulting 6-morpholinyl nucleoside was used to estimate the efficiency of polymer loading. ^(b)The resulting 6-morpholinyl product contained about 5% of an impurity (as assessed by ¹H NMR). ^(c)The reaction was significantly incomplete and about 48% 22 was left (as assessed by ¹H NMR).

In Reaction Scheme 8, the polymer support is commercially available 1% cross-linked polystyrene-co-divinylbenzene with a HOBT loading of 1.02 mmol/g of polymer. After the reaction leading to attachment of the nucleoside to the polymer support, isolation of the polymer and washing with a series of solvents affords the appropriate polymer-supported nucleosides for further reactions. The polymer loading was in the range of 0.24-0.33 mmol/g as determined by cleavage of the nucleoside from the polymer support via the use of morpholine in the presence of Cs₂CO₃ in 1,2-dimethoxyethane.

The synthesis of polymer-bound HOBT has been reported in the literature. For example, see Pop, I. E.; Déprez, B. P.; Tartar, A. L. J. Org. Chem. 1997, 62, 2594-2603. There are various known methods for the attachment of HOBT to a polymer. See Kalir, R., Warshawsky, A., Fridkin, M., Patchornik, A. Eur. J. Biochem. 1975, 59, 55-61; Huang, W., Kalivretenos, A. G. Tetrahedron Lett. 1995, 36, 9113-9116; Dendrinos, K., Jeong, J., Huang, W., Kalivretenos, A. G. Chem. Commun. 1998, 499-500; Dendrinos, K. G., Kalivretenos, A. G. J. Chem. Soc., Perkin Trans. 1, 1998, 1463-1464; Dendrinos, K. G., Kalivretenos, A. G. Tetrahedron Lett. 1998, 39, 1321-1324; Chinchilla, R., Dodsworth, D. J., Nájera, C., Soriano, J. M. Tetrahedron Lett. 2000, 41, 2463-2466; and Scicinski, J. J., Congreve, M. S., Jamieson, C., Ley, S. V., Newman, E. S., Vinader, V. M., Carr, R. A. E. J. Combi. Chem. 2000, 3, 387-396.

In addition, polymer-bound HOBT is commercially available. For example, commercially available polymer-supported HOBT include

Any polymeric support can be attached to the HOBT entity if suitable starting materials for assembly of the HOBT core as well as complementary polymer supports are available. Some representative examples from the literature are shown below in Reaction Scheme 9.

Examples of other possible linkers are provided below in Reaction Scheme 10.

Reaction Scheme 10 involves displacement chemistry with coupling partners where A is Cl, Br, or I and B is OH, SH, or NHR, leading to products where D is O, S or NR. Correspondingly, when A is OH, SH or NHR and B is Cl, Br or I, then D is O in the resulting compounds. Alternatively, a Mitsunobu reaction between suitable coupling partners can also lead to the requisite final products.

Polymer supported reagents 30 and 31 were subjected to displacement reactions with a selection of nucleophiles. The results from these reactions are collected in Table 3 below.

TABLE 3 Reaction of polymer-supported nucleosides with nucleophiles

Entry Compound Nucleophile Condition Product, yield 1 30 CH₃OH CH₃OH, Cs₂CO₃, rt, 24 h 91% 2 30 CH₃CH₂OH CH₃CH₂OH, Cs₂CO₃, rt, 51% 36 h CH₃CH₂OH, Cs₂CO₃, 87% 78° C., 15 h 3 30 (CH₃)₂CHOH (CH₃)₂OH, Cs₂CO₃, 82° C., No reaction 15 h 4 30

DME, Cs₂CO₃, 85° C., 1 h 41%^(a) 5 30

DME, Cs₂CO₃, 85° C., 15 h 54% 6 30

DME, Cs₂CO₃, 85° C., 15 h 68% 7 30

DME, Cs₂CO₃, 85° C, 15 h 49%^(a) 8 30

DME, Cs₂CO₃, 85° C., 8 h 39%^(a) 9 30 31

DME, Cs₂CO₃, rt (24 h) and then 85° C. (20 h) DME, Cs₂CO₃, rt, 24 h 87%^(a) 46%^(a) 10 30 (CH₃)₂NH DME, rt, 24 h quantitative 31 DME, rt, 24 h quantitative 11 30

DME, rt, 24 h quantitative 12 30 31

DME, rt, 24 h DME, rt, 24 h quantitative quantitative 13 30 30 30 30 31

DME, Cs₂CO₃, rt, 34 h DME, Cs₂CO₃, 85° C., 15 h CH₂Cl₂, Cs₂CO₃, rt, 34 h DME, rt, 24 h DME, rt, 24 h quantitative quantitative 95% quantitative quantitative 14 30

DME, Cs₂CO₃, 85° C., 15 h 69% 15 30 31

DME, rt, 24 h DME, rt, 24 h quantitative 92% ^(a)Product formation in these cases is accompanied by 8-31% of 32i as seen in the ¹H NMR or by TLC analysis of the crude reaction products. Uses of Convertible Nucleoside Derivatives

Convertible nucleosides provide a facile approach to the synthesis of modified nucleosides that are useful for biochemical and biological studies. For example, convertible nucleoside derivatives can be incorporated into DNA. In such a case, the nucleoside may, for example, be labeled. See Example 36.

In another utility, convertible nucleosides can also be used to synthesize 1,N⁶-ethano- and 1,N⁶-propano-2′-deoxyadenosine analogues. Alkylating nitrosoureas as a class are used in the chemotherapy of solid tumors and leukemias. Among these, 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU, carmustine) is a potent analogue for the treatment of brain tumors. The DNA cross-linking properties of 2-chloroethyl-1-nitrosoureas are associated with their cell lethality. However, the reaction of BCNU with DNA results in a variety of other alkylation products, one of which is 1,N⁶-ethano-2′-deoxyadenosine. This compound is related to the 1,N⁶-ethenoadenine derivatives that are formed from the reaction of vinyl chloride with 9-methyladenine or adenosine. Since the hydrogen bonding sites of 2′-deoxyadenosine are directly involved in the ring formation, synthetic access to 1,N⁶-ethano-2′-deoxyadenosine is useful to understand its biological consequences. See Example 37.

EXAMPLES

The specific examples describe a preferred method for synthesizing the compounds of the present invention. The scope of this invention is not to be in any way limited by the examples set forth herein.

Reactions were monitored by TLC (silica gel, 250 μm) and column chromatographic purifications were performed on 200-300 mesh silica gel. Solvents used for eluting the compounds, as well as TLC conditions and R_(f) values, are provided under individual compound headings. All other reagents were obtained from commercial sources and used without further purification. ¹H NMR spectra were recorded at 500 MHz and ¹³C NMR were recorded at 126 MHz. ³¹P NMR spectra (202 MHz) were referenced to 85% H₃PO₄ as an external standard. All spectra were appropriately referenced. Chemical shifts are reported in δ parts per million, and coupling constants are in hertz. The sugar protons are numbered 1′-5′ beginning at the anomeric carbon and proceeding via the carbon chain to the primary carbinol carbon.

Example 1 Synthesis of 9-(2-Deoxy-3,5-bis-O-(tert-butyldimethylsilyl)-β-D-erythro-pentofuranosyl)purin-6-yloxy-(tris(dimethylamino)phosphonium)hexafluorophosphate

In a clean, dry reaction vial equipped with a stirring bar were placed 3′,5′-bis-O-(tert-butyldimethylsilyl)-2′-deoxyinosine (23) (0.100 g, 0.208 mmol) and BOP (0.184 g, 0.416 mmol). Dry THF (2.0 mL) and DIPEA (54.3 μL, 0.312 mmol) were added and the mixture was allowed to stir at room temperature for 4 h and then evaporated. The crude material was taken up in CH₂Cl₂ and washed with water. The organic layer was separated, dried over Na₂SO₄ and concentrated. Purification by preparative thin layer chromatography (SiO₂, 5% MeOH in CH₂Cl₂) afforded ˜10 mg (6% yield) of the product as a clear gum. R_(f) (5% MeOH in CH₂Cl₂)=0.26. ¹H NMR (500 MHz, CDCl₃): δ 8.68 (s, 1H, Ar—H), 8.50 (s, 1H, Ar—H), 6.54 (t, 1H, H-1′, J=6.4), 4.63 (m, 1H, H-3′), 4.06 (q, 1H, H-4′, J=3.3), 3.89 (dd, 1H, H-5′, J=11.2, 3.7), 3.79 (dd, 1H, H-5′, J=11.2, 2.9), 2.66 (app quint, 1H, H-2′, J_(app)˜6.4), 2.52 (ddd, 1H, H-2′, J=13.2, 5.9, 3.9), 2.92 (d, 18H, NCH₃, J_(H—P)=11.2), 0.92, 0.90 (2 s, 18H, tert-Bu), 0.11, 0.09, 0.08 (3 s, 12H, SiCH₃). ¹³C NMR (126 MHz, CDCl₃): δ 154.4, 152.7, 151.5, 144.5, 123.0, 88.4, 85.2, 71.9, 62.7, 41.4, 37.3 (d, J_(C—P)=4.5), 25.9, 25.7, 18.4, 18.0, −4.7, −4.8, −5.4, −5.5. ³¹P NMR (202 MHz, CDCl₃): δ 35.44 (s, P[N(CH₃)₂]₃), −143.31 (septet, PF₆, J_(P,F)=712).

Example 2 Synthesis of O⁶-(Benzotriazol-1-yl)-3′,5′-bis-O-(tert-butyldimethylsilyl)-2′-deoxyinosine (26)

In a 50 mL round-bottomed flask equipped with a stirring bar were placed 3′,5′-bis-O-(tert-butyldimethylsilyl)-2′-deoxyinosine (22) (1.005 g, 2.090 mmol) and BOP (1.850 g, 4.181 mmol). THF (20 mL) and DIPEA (0.55 mL, 3.135 mmol) were added and the mixture was allowed stir at room temperature for 23 h. The mixture was evaporated and CH₂Cl₂ (50 mL) added. The mixture was washed with water, dried over Na₂SO₄ and concentrated. Chromatographic purification (SiO₂, elution with 20% EtOAc in hexanes) afforded 1.038 g (83% yield) of compound 26 as a white foam. R_(f) (20% EtOAc in hexanes)=0.14. ¹H NMR (500 MHz, CDCl₃): δ 8.54 (s, 1H, Ar—H), 8.41 (s, 1H, Ar—H), 8.14 (d, 1H, Ar—H, J=8.3), 7.55-7.41 (m, 3H, Ar—H), 6.55 (t, 1H, H-1′, J=6.1), 4.65 (m, 1H, H-3′), 4.06 (q, 1H, H-4′, J=3.1), 3.92 (dd, 1H, H-5′, J=11.2, 3.9), 3.80 (dd, 1H, H-5′, J=11.2, 2.7), 2.65 (app quint, 1H, H-2′, J_(app)˜6.3), 2.52 (m, 1H, H-2′), 0.93, 0.92 (2 s, 18H, tert-Bu), 0.11 (s, 12H, SiCH₃). ¹³C NMR (126 MHz, CDCl₃): δ 159.0, 153.6, 151.3, 143.5, 128.9, 128.7, 124.8, 120.6, 120.0, 108.6, 88.2, 85.0, 71.6, 62.6, 41.7, 25.9, 25.7, 18.4, 18.0, −4.7, −4.8, −5.4, −5.5. FAB HRMS calcd for C₂₈H₄₄N₇O₄Si₂ (M⁺+H) 598.2993. found 598.2986.

Alternate Synthesis of O⁶-(Benzotriazol-1-yl)-3′,5′-bis-O-(tert-butyldimethylsilyl)-2′-deoxyinosine (26)

In a 50 mL round-bottom flask equipped with a stirring bar were placed PPh₃ (0.823 g, 3.138 mmol) and I₂ (0.800 g, 3.152 mmol) in dry CH₂Cl₂ (11.0 mL) and the mixture was stirred at room temperature for 20 min. DIPEA (1.5 mL, 8.62 mmol) and 3′,5′-bis-O-(tert-butyldimethylsilyl)-2′-deoxyinosine (1a) (0.500 g, 1.040 mmol) were added, and the mixture was allowed to stir at room temperature for 26 h. To this mixture was added HOBT (0.211 g, 1.561 mmol) and the reaction was allowed to continue and was complete in 22 h. The crude material was evaporated and chromatographic purification (SiO₂, elution with 20% EtOAc in hexanes) afforded 0.578 g (93%) of compound 26 as a beige foam.

Example 2a Synthesis of O⁶-(Triazolyl-1-yl)-3′,5′-bis-O-(tert-butyldimethylsilyl)-2′-deoxyinosine (26a)

In a 50 mL round-bottomed flask equipped with a stirring bar are placed 3′,5′-bis-O-(tert-butyldimethylsilyl)-2′-deoxyinosine (22) and triazolyl-1-yloxy-tris(dimethylamino)phosphonium. THF and DIPEA are added and the mixture is stirred at room temperature for 23 h. The mixture is evaporated and CH₂Cl₂ (50 mL) is added. The mixture is washed with water. Then the mixture is dried over Na₂SO₄. Finally, the mixture is concentrated.

Example 2b Synthesis of O⁶-(Imidazolyl-1-yl)-3′,5′-bis-O-(tert-butyldimethylsilyl)-2′-deoxyinosine (26b)

In a 50 mL round-bottomed flask equipped with a stirring bar are placed 3′,5′-bis-O-(tert-butyldimethylsilyl)-2′-deoxyinosine (22) and imidazolyl-1-yloxy-tris(dimethylamino)phosphonium. THF and DIPEA are added and the mixture is stirred at room temperature for 23 h. The mixture is evaporated and CH₂Cl₂ (50 mL) is added. The mixture is washed with water. Then the mixture is dried over Na₂SO₄. Finally, the mixture is concentrated.

Example 3 Synthesis of O⁶-(Benzotriazol-1-yl)-2′,3′,5′-tris-O-(tert-butyldimethylsilyl)inosine (27)

As described for the synthesis of 26, 27 was prepared by a reaction between 2′,3′,5′-tris-O-(tert-butyldimethylsilyl)inosine (23) (3.055 g, 5.00 mmol), BOP (4.425 g, 10.0 mmol) and DIPEA (1.31 mL, 7.5 mmol) in dry THF (50.0 mL). Chromatographic purification (SiO₂, elution with 20% EtOAc in hexanes) afforded 2.898 g (80% yield) of compound 27 as a white, foamy solid. R_(f) (20% EtOAc in hexanes)=0.32. ¹H NMR (500 MHz, CDCl₃): δ 8.63 (s, 1H, Ar—H), 8.40 (s, 1H, Ar—H), 8.15 (d, 1H, Ar—H, J=8.3), 7.56-7.45 (m, 3H, Ar—H), 6.16 (d, 1H, H-1′, J=4.4), 4.58 (t, 1H; H-2′, J=4.4), 4.34 (t, 1H, H-3′, J=4.2), 4.18 (app q, 1H, H-4′, J_(app)˜3.1), 4.06 (dd, 1H, H-5′, J=11.7, 3.4), 3.82 (dd, 1H, H-5′, J=11.7, 2.4), 0.98, 0.94, 0.82 (3 s, 27H, tert-Bu), 0.17, 0.16, 0.11, 0.10, 0.0, −0.17 (6 s, 18H, SiCH₃). ¹³C NMR (126 MHz, CDCl₃): δ 159.0, 153.9, 151.4, 143.9, 143.5, 129.0, 128.7, 124.8, 120.6, 120.0, 108.6, 88.9, 85.5, 76.4, 71.6, 62.2, 26.1, 25.8, 25.6, 18.5, 18.0, 17.8, −4.4, −4.7, −4.73, −5.0, −5.3, −5.4. FAB HRMS calcd for C₃₄H₅₈N₇O₅Si₃ (M⁺+H) 728.3807. found 728.3818.

Alternate Synthesis of O⁶-(Benzotriazol-1-yl)-2′,3′,5-tris-O-(tert-butyldimethylsilyl)inosine (27)

As described for the synthesis of O⁶-(benzotriazol-1-yl)-3′,5′-bis-O-(tert-butyldimethylsilyl)-2′-deoxyinosine, this ribose derivative was prepared by a reaction of PPh₃ (0.645 g, 2.459 mmol), I₂ (0.632 g, 2.490 mmol), DIPEA (1.2 mL, 6.89 mmol), 2′,3′,5′-tris-O-(tert-butyldimethylsilyl)inosine (1b) (0.500 g, 0.818 mmol) and HOBT (0.166 g, 1.228 mmol) in dry CH₂Cl₂ (9.0 mL). Chromatographic purification (SiO₂, elution with 20% EtOAc in hexanes) afforded 0.537 g (90%) of compound 4b as a yellowish-white foam.

Example 4 Synthesis of O⁶-(Benzotriazol-1-yl)-2′-deoxyinosine (28)

In a 50 mL round-bottomed flask equipped with a stirring bar were placed 2′-deoxyinosine 24 (0.504 g, 2.00 mmol) and BOP (1.770 g, 4.00 mmol). DMF (20 mL) and DIPEA (0.70 mL, 4.00 mmol) were added and the mixture was allowed to stir at room temperature for 26 h. The reaction mixture was evaporated with toluene several times. The crude product was dissolved in EtOAc and washed with water. The organic layer was separated, dried over Na₂SO₄ and concentrated. Chromatographic purification (SiO₂, elution with 10% MeOH in CH₂Cl₂) afforded 0.421 g (57% yield) of compound 28 as a pale brownish-white foam. R_(f) (10% MeOH in CH₂Cl₂)=0.38. ¹H NMR (500 MHz, CDCl₃): δ 8.43 (s, 1H, Ar—H), 8.24 (s, 1H, Ar—H), 8.16-8.14 (m, 1H, Ar—H), 7.57-7.54 (m, 1H, Ar—H), 7.49-7.46 (m, 1H, Ar—H), 6.46 (dd, 1H, H-1′, J=9.2, 5.5), 5.10 (dd, 1H, OH, J=11.3, 2.3, CD₃OD exchangeable), 4.83 (br m, 1H, H-3′), 4.25 (br s, 1H, H-4′), 3.97 (dt, 1H, H-5′, J=12.8, 2.0), 3.82 (app td, 1H, H-5′, J_(app)˜11.9, 1.8), 3.07 (ddd, 1H, H-2′, J=13.4, 9.5, 4.9), 2.42 (dd, 1H, H-2′, J=13.6, 5.7), 2.05 (d, 1H, OH, CD₃OD exchangeable). ¹³C NMR (126 MHz, DMSO-d₆): δ 159.1, 153.1, 151.1, 144.8, 143.2, 129.1, 128.8, 125.2, 120.5, 120.3, 108.7, 88.9, 86.9, 72.2, 62.7, 40.9. FAB HRMS calcd for C₁₆H₁₆N₇O₄ (M⁺+H) 370.1264. found 370.1258.

Example 5 Synthesis of O⁶-(Benzotriazol-1-yl)inosine (29)

In a reaction vial equipped with a stirring bar were placed inosine 25 (0.100 g, 0.373 mmol) and BOP (0.330 g, 0.746 mmol). DMF (3.7 mL) and DIPEA (97.3 μL, 0.559 mmol) were added, the reaction vial was flushed with N₂ and the mixture allowed to stir at room temperature for 68 h. To the reaction mixture water was added and the mixture was extracted with CH₂Cl₂. The organic layer was separated, washed with brine, dried over Na₂SO₄ and concentrated. Since the crude product contained residual DMF, toluene was added and evaporated several times. Chromatographic purification (SiO₂, elution with 5% MeOH in CH₂Cl₂) afforded 76 mg (53% yield) of 29 as a white powder. R_(f) (5% MeOH in CH₂Cl₂)=0.09. ¹H NMR (500 MHz, DMSO-d₆): δ 8.95 (s, 1H, Ar—H), 8.53 (s, 1H, Ar—H), 8.21 (d, 1H, Ar—H, J=8.8), 7.80 (d, 1H, Ar—H, J=8.3), 7.66 (t, 1H, Ar—H, J=7.6), 7.56 (t, 1H, Ar—H, J=7.6), 6.09 (d, 1H, H-1′, J=5.4), 5.55 (d, 1H, OH, J=5.9, D₂O exchangeable), 5.24 (d, 1H, OH, J=5.4, D₂O exchangeable), 5.07 (t, 1H, OH, J=5.6, D₂O exchangeable), 4.62 (q, 1H, H-2′, J=5.4), 4.21 (q, 1H, H-3′, J=4.7), 4.01 (m, 1H, H-4′), 3.71 (m, 1H, H-5′), 3.60 (m, 1H, H-5′). ¹³C NMR (126 MHz, DMSO-d₆): δ 159.0, 154.8, 151.9, 146.1, 143.5, 130.1, 129.3, 126.1, 120.7, 119.8, 110.2, 88.9, 86.5, 74.7, 70.9, 61.8. FAB HRMS calcd for C₁₆H₁₆N₇O₅ (M⁺+H) 386.1213. found 386.1191.

Example 6 Synthesis of 3′,5′-Bis-O-(tert-butyldimethylsilyl)-O⁶-methyl-2′-deoxyinosine

In a clean, dry reaction vial equipped with a stirring bar were placed O⁶-(benzotriazol-1-yl)-3′,5′-bis-O-(tert-butyldimethylsilyl)-2′-deoxyinosine (26) (59.8 mg, 0.100 mmol), Cs₂CO₃ (65.2 mg, 0.200 mmol) and methanol (1.0 mL). The reaction mixture was flushed with N₂ and stirred at room temperature for 1 h after which the mixture was evaporated to dryness. Chromatographic purification (SiO₂, elution with 20% EtOAc in hexanes) afforded 38 mg (77% yield) of the title compound as a clear gum. R_(f) (20% EtOAc in hexanes)=0.12. ¹H NMR (500 MHz, CDCl₃): δ 8.52 (s, 1H, Ar—H), 8.27 (s, 1H, Ar—H), 6.49 (t, 1H, H-1′, J=6.3), 4.62 (m, 1H, H-3′), 4.18 (s, 3H, OCH₃), 4.01 (q, 1H, H-4′, J=3.4), 3.87 (dd, 1H, H-5′, J=11.2, 3.9), 3.77 (dd, 1H, H-5′, J=11.2, 2.9), 2.62 (app quint, 1H, H-2′, J_(app)˜6.3), 2.45 (ddd, 1H, H-2′, J=13.2, 6.4, 3.9), 0.91 (s, 18H, tert-Bu), 0.09, 0.08 (2 s, 12H, SiCH₃). ¹³C NMR (126 MHz, CDCl₃): δ 161.1, 152.0, 151.5, 140.6, 122.0, 88.0, 84.5, 71.9, 62.8, 54.0, 41.4, 25.9, 25.7, 18.4, 17.9, −4.7, −4.8, −5.5, −5.6. FAB HRMS calcd for C₂₃H₄₃N₄O₄Si₂ (M⁺+H) 495.2823. found 495.2798.

Example 7 Synthesis of 3′,5′-Bis-O-(tert-butyldimethylsilyl)-O⁶-ethyl-2′-deoxyinosine

As described for the synthesis of 3′,5′-bis-O-(tert-butyldimethylsilyl)-O⁶-methyl-2′-deoxyinosine, the ethyl derivative was prepared by a reaction between O⁶-(benzotriazol-1-yl)-3′,5′-bis-O-(tert-butyldimethylsilyl)-2′-deoxyinosine (26) (59.8 mg, 0.100 mmol) and EtOH (1 mL) in the presence of Cs₂CO₃ (65.2 mg, 0.200 mmol) over 1 h. Chromatographic purification (SiO₂, elution with 20% EtOAc in hexanes) afforded 48.2 mg (95% yield) of the title compound as a clear gum. R_(f) (20% EtOAc in hexanes)=0.16. ¹H NMR (500 MHz, CDCl₃): δ 8.50 (s, 1H, Ar—H), 8.26 (s, 1H, Ar—H), 6.50 (t, 1H, H-1′, J=6.4), 4.65 (q, 2H, OCH₂, J=7.0), 4.61 (m, 1H, H-3′), 4.01 (q, 1H, H-4′, J=3.4), 3.87 (dd, 1H, H-5′, J=11.2, 3.9), 3.77 (dd, 1H, H-5′, J=11.2, 2.9), 2.61 (quint, 1H, H-2′, J=6.3), 2.44 (ddd, 1H, H-2′, J=12.9, 6.1, 3.9), 1.50 (t, 3H, CH₃, J=7.3), 0.91 (s, 18H, tert-Bu), 0.09, 0.08 (2 s, 12H, SiCH₃). ¹³C NMR (126 MHz, CDCl₃): δ 160.8, 152.0, 151.5, 140.5, 121.9, 87.9, 84.4, 71.8, 63.1, 62.7, 41.5, 26.0, 25.7, 18.4, 18.0, 14.5, −4.7, −4.8, −5.4, −5.5. FAB HRMS calcd for C₂₄H₄₅N₄O₄Si₂ (M⁺+H) 509.2979. found 509.2953.

Example 8 Synthesis of 3′,5′-Bis-O-(tert-butyldimethylsilyl)-O⁶-isopropyl-2′-deoxyinosine

As described for the synthesis of 3′,5′-bis-O-(tert-butyldimethylsilyl)-O⁶-methyl-2′-deoxyinosine, the isopropyl derivative was prepared by a reaction between O⁶-(benzotriazol-1-yl)-3′,5′-bis-O-(tert-butyldimethylsilyl)-2′-deoxyinosine (26) (59.8 mg, 0.100 mmol) and 2-propanol (1 mL) in the presence of Cs₂CO₃ (65.2 mg, 0.200 mmol) over 10 h. Chromatographic purification (SiO₂, elution with 20% EtOAc in hexanes) afforded 44.1 mg (84% yield) of the title compound as a clear gum. R_(f) (20% EtOAc in hexanes)=0.31. ¹H NMR (500 MHz, CDCl₃): δ 8.50 (s, 1H, Ar—H), 8.23 (s, 1H, Ar—H), 6.49 (t, 1H, H-1′, J=6.3), 5.67 (septet, 1H, —CH—, J=6.3), 4.61 (m, 1H, H-3′), 4.02 (m, 1H, H-4′), 3.87 (dd, 1H, H-5′, J=11.2, 3.9), 3.78 (dd, 1H, H-5′, J=10.7, 2.9), 2.63 (app quint, 1H, H-2′, J_(app)˜6.3), 2.44 (ddd, 1H, H-2′, J=13.2, 5.9, 3.9), 1.47 (d, 6H, CH₃, J=6.5), 0.91 (s, 18H, tert-Bu), 0.10, 0.09 (2 s, 12H, SiCH₃). ¹³C NMR (126 MHz, CDCl₃): δ 160.5, 152.0, 151.5, 140.3, 122.0, 87.9, 84.4, 71.9, 71.2, 62.8, 41.4, 26.0, 25.7, 22.0, 18.4, 18.0, −4.7, −4.8, −5.4, −5.5. FAB HRMS calcd for C₂₅H₄₇N₄O₄Si₂ (M⁺+H) 523.3136. found 523.3130.

Example 9 Synthesis of O⁶-Isopropyl-2′,3′,5′-tris-O-(tert-butyldimethylsilyl)inosine

As described for the synthesis of 3′,5% bis-O-(tert-butyldimethylsilyl)-O⁶-methyl-2′-deoxyinosine, this isopropyl derivative was prepared by a reaction between O⁶-(benzotriazol-1-yl)-2′,3′,5′-tris-O-(tert-butyldimethylsilyl)-2′-deoxyinosine (27) (71.8 mg, 0.099 mmol) and 2-propanol (1 mL) in the presence of Cs₂CO₃ (65.2 mg, 0.200 mmol) over 24 h at room temperature and then at 85° C. for 3 h. Chromatographic purification (SiO₂, elution with 20% EtOAc in hexanes) afforded 45.6 mg (70% yield) of the title compound as a clear gum. R_(f) (20% EtOAc in hexanes)=0.59. ¹H NMR (500 MHz, CDCl₃): δ 8.49 (s, 1H, Ar—H), 8.27 (s, 1H, Ar—H), 6.08 (d, 1H, H-1′, J=5.4), 5.66 (septet, 1H, —CH—, J=6.3), 4.64 (t, 1H, H-2′, J=4.6), 4.32 (t, 1H, H-3′, J=3.9), 4.13 (q, 1H, H-4′, J=3.3), 4.02 (dd, 1H, H-5′, J=11.2, 3.9), 3.79 (dd, 1H, H-5′, J=11.2, 2.7), 1.48 (d, 3H, CH₃, J=6.4), 1.47 (d, 3H, CH₃, J=6.4), 0.95, 0.93, 0.79 (3 s, 27H, tert-Bu), 0.14, 0.13, 0.10, 0.09, −0.05, −0.23 (6 s, 18H, SiCH₃). ¹³C NMR (126 MHz, CDCl₁): δ160.5, 152.0, 151.9, 140.8, 122.1, 88.3, 85.4, 76.0, 71.9, 70.2, 62.5, 26.1, 25.8, 25.6, 22.0, 18.5, 18.1, 17.8, −4.4, −4.7, −4.73, −5.1, −5.4. FAB HRMS calcd for C₃₁H₆₁N₄O₅Si₃ (M⁺+H) 653.3950. found 653.3944.

Example 10 Synthesis of O⁶-Allyl-3′,5′-bis-O-(tert-butyldimethylsilyl)-2′-deoxyinosine

As described for the synthesis of 3′,5-bis-O-(tert-butyldimethylsilyl)-O⁶-methyl-2′-deoxyinosine, the allyl derivative was prepared by a reaction between O⁶-(benzotriazol-1-yl)-3′,5-bis-O-(tert-butyldimethylsilyl)-2′-deoxyinosine (26) (59.8 mg, 0.100 mmol) and allyl alcohol (1 mL) in the presence of Cs₂CO₃ (65.2 mg, 0.200 mmol) over 2 h. Chromatographic purification (SiO₂, elution with 20% EtOAc in hexanes) afforded 46.4 mg (89% yield) of the title compound as a clear gum. R_(f) (20% EtOAc in hexanes)=0.29. ¹H NMR (500 MHz, CDCl₃): δ 8.51 (s, 1H, Ar—H), 8.27 (s, 1H, Ar—H), 6.50 (t, 1H, H-1′, J=6.4), 6.16 (m, 1H, —CH═), 5.45 (dd, 1H, ═CH_(trans), J=17.1, 1.5), 5.29 (d, 1H, ═CH_(cis), J=10.7), 5.12 (d, 2H, OCH₂, J=5.4), 4.61 (m, 1H, H-3′), 4.02 (q, 1H, H-4′, J=3.4), 3.87 (dd, 1H, H-5′, J=11.2, 3.9), 3.77 (dd, 1H, H-5′, J=11.2, 2.9), 2.61 (app quint, 1H, H-2′, J_(app)˜6.3), 2.44 (ddd, 1H, H-2′, J=12.9, 6.1, 3.9), 0.91 (s, 18H, tert-Bu), 0.09, 0.08 (2 s, 12H, SiCH₃). ¹³C NMR (126 MHz, CDCl₃): δ 160.3, 151.9, 151.6, 140.6, 132.4, 121.9, 118.5, 87.9, 84.4, 71.8, 67.5, 62.7, 41.4, 26.0, 25.7, 18.4, 18.0, −4.7, −4.8, −5.4, −5.5. FAB HRMS calcd for C₂₅H₄₅N₄O₄Si₂ (M⁺+H) 521.2979. found 521.2974.

Example 11 Synthesis of 3′,5′-Bis-O-(tert-butyldimethylsilyl)-O⁶-phenyl-2′-deoxyinosine

In a clean, dry reaction vial equipped with a stirring bar were placed O⁶-(benzotriazol-1-yl)-3′,5′-bis-O-(tert-butyldimethylsilyl)-2′-deoxyinosine (26) (63.2 mg, 0.106 mmol), Cs₂CO₃ (68.9 mg, 0.211 mmol) and phenol (19.9 mg, 0.211 mmol). Dry toluene (1.0 mL) was added and the reaction mixture was flushed with N₂ and the mixture was allowed to stir at 105° C. for 2 h. The reaction mixture was filtered through Celite, the residue washed with Et₂O and the filtrate evaporated to dryness. Chromatographic purification (SiO₂, elution with 20% EtOAc in hexanes) afforded 50.5 mg (86% yield) of the title compound as a clear gum. R_(f) (20% EtOAc in hexanes)=0.21. ¹H NMR (500 MHz, CDCl₃): δ 8.49 (s, 1H, Ar—H), 8.40 (s, 1H, Ar—H), 7.45 (app t, 2H, Ar—H, J_(app)˜7.8), 7.29-7.26 (m, 3H, Ar—H), 6.53 (t, 1H, H-1′, J=6.3), 4.64 (m, 1H, H-3′), 4.04 (q, 1H, H-4′, J=3.4), 3.90 (dd, 1H, H-5′, J=11.2, 3.9), 3.70 (dd, 1H, H-5′, J=11.2, 2.7), 2.65 (app quint, 1H, H-2′, J_(app)˜6.3), 2.48 (ddd, 1H, H-2′, J=13.2, 6.1, 4.1), 0.92, 0.91 (2 s, 18H, tert-Bu), 0.10 (s, 12H, SiCH₃). ¹³C NMR (126 MHz, CDCl₃): δ 160.2, 152.5, 152.4, 152.0, 141.6, 129.6, 125.7, 122.1, 121.9, 88.0, 84.6, 71.8, 62.7, 41.5, 26.0, 25.7, 18.4, 18.0, −4.7, −4.8, −5.4, −5.5. FAB HRMS calcd for C₂₈H₄₅N₄O₄Si₂ (M⁺+H) 557.2979. found 557.2978.

Example 12 Synthesis of 3′,5-Bis-O-(tert-butyldimethylsilyl)-O⁶-(4-nitrophenyl)-2′-deoxyinosine

In a clean, dry reaction vial equipped with a stirring bar were placed O⁶-(benzotriazol-1-yl)-3′,5′-bis-O-(tert-butyldimethylsilyl)-2′-deoxyinosine (26) (40 mg, 0.067 mmol), Cs₂CO₃ (43.6 mg, 0.134 mmol) and 4-nitrophenol (18.6 mg, 0.134 mmol). Dry DME (0.7 mL) was added and the reaction mixture was flushed with N₂ and the mixture was allowed to stir at 85° C. for 2 h. The reaction mixture was diluted with EtOAc and washed with 0.1 N aq NaOH followed by brine. The organic layer was dried over Na₂SO₄, and evaporated to dryness. Chromatographic purification (SiO₂, elution with 50% EtOAc in hexanes) afforded 31.3 mg (78% yield) of the title compound as a yellow gum. R_(f) (5% MeOH in CH₂Cl₂)=0.58. ¹H NMR (500 MHz, CDCl₃): δ 8.51 (s, 1H, Ar—H), 8.46 (s, 1H, Ar—H), 8.34 (d, 2H, Ar—H, J=9.3), 7.47 (d, 2H, Ar—H, J=8.8), 6.55 (t, 1H, H-1′, J=6.4), 4.65 (m, 1H, H-4′, J=3.4), 3.91 (dd, 1H, H-5′, J=11.2, 3.4), 3.80 (dd, 1H, H-5′, J=11.2, 2.9), 2.65 (app quint, 1H, H-2′, J_(app)˜6.3), 2.50 (ddd, 1H, H-2′, J=13.2, 6.1, 4.2), 0.92 (s, 18H, tert-Bu), 0.113, 0.11 (2 s, 12H, SiCH₃). ¹³C NMR (126 MHz, CDCl₁): δ 158.9, 157.4, 153.1, 151.6, 145.2, 142.4, 125.3, 122.3, 122.2, 88.1, 84.8, 71.8, 62.7, 41.6, 26.0, 25.7, 18.4, 18.0, −4.7, −4.8, −5.4, −5.5. FAB HRMS calcd for C₂₈H₄₄N₅O₆Si₂ (M⁺+H) 602.2830. found 602.2813.

Example 13 Synthesis of O⁶-(4-Nitrophenyl)-2′,3′,5′-tris-O-(tert-butyldimethylsilyl)inosine

As described for the synthesis of 3′,5′-bis-O-(tert-butyldimethylsilyl)-O⁶-(4-nitrophenyl)-2′-deoxyinosine, this 4-nitrophenyl derivative was prepared by a reaction between O⁶-(benzotriazol-1-yl)-2′,3′,5′-tris-O-(tert-butyldimethylsilyl)inosine (27) (71.8 mg, 0.099 mmol) and 4-nitrophenol (27.8 mg, 0.200 mmol) in the presence of Cs₂CO₃ (65.2 mg, 0.200 mmol) in dry DME (1.0 mL) at 85° C. over 1 h. Chromatographic purification (SiO₂, elution with 20% EtOAc in hexanes) afforded 59.5 mg (81% yield) of the title compound as a clear gum. R_(f) (20% EtOAc in hexanes)=0.43. ¹H NMR (500 MHz, CDCl₃): δ 8.53 (s, 1H, Ar—H), 8.51 (s, 1H, Ar—H), 8.35-8.33 (m, 2H, Ar—H), 7.48 (d, 2H, Ar—H, J=9.3), 6.15 (d, 1H, H-1′, J=4.9), 4.61 (t, 1H, H-2′, J=4.6), 4.34 (t, 1H, H-3′, J=4.2), 4.17 (q, 1H, H-4′, J=3.3), 4.05 (dd, 1H, H-5′, J=11.5, 3.7), 3.82 (dd, 1H, H-5′, J=11.5, 2.2), 0.97, 0.94, 0.81 (3 s, 27H, tert-Bu), 0.17, 0.16, 0.11, 0.10, −0.01, −0.18 (6 s, 18H, SiCH₃). ¹³C NMR (126 MHz, CDCl₃): δ 158.8, 157.3, 153.3, 151.7, 145.1, 142.8, 125.4, 122.4, 122.1, 88.6, 85.5, 76.4, 71.7, 62.4, 26.1, 25.8, 25.6, 18.5, 18.1, 17.8, −4.4, −4.7, −4.72, −5.0, −5.3, −5.4. FAB HRMS calcd for C₃₄H₅₈N₅O₇Si₃ (M⁺+H) 732.3644. found 732.3629.

Example 14 Synthesis of 3′,5′-Bis-O-(tert-butyldimethylsilyl)-O⁶-(3-cyanophenyl)-2′-deoxyinosine

As described for the synthesis of 3′,5′-bis-O-(tert-butyldimethylsilyl)-O⁶-(4-nitrophenyl)-2′-deoxyinosine, this 3-cyanophenyl derivative was prepared by a reaction between O⁶-(benzotriazol-1-yl)-3′,5′-bis-O-(tert-butyldimethylsilyl)-2′-deoxyinosine (26) (59.8 mg, 0.100 mmol) and 3-cyanophenol (13.1 mg, 0.110 mmol) in the presence of Cs₂CO₃ (65.2 mg, 0.200 mmol) in dry DME (1.0 mL) at 85° C. over 2 h. Chromatographic purification (SiO₂, elution with 20% EtOAc in hexanes) afforded 47.5 mg (82% yield) of the title compound as a clear gum. R_(f) (50% EtOAc in hexanes)=0.58. ¹H NMR (500 MHz, CDCl₃): δ 8.49 (s, 1H, Ar—H), 8.45 (s, 1H, Ar—H), 7.62-7.54 (m, 4H, Ar—H), 6.54 (t, 1H, H-1′, J=6.4), 4.64 (m, 1H, H-3′), 4.05 (q, 1H, H-4′, J=3.4), 3.91 (dd, 1H, H-5′, J=11.2, 3.9), 3.80 (dd, 1H, H-5′, J=11.2, 3.9), 2.64 (app quint, 1H, H-2′, J_(app)˜6.3), 2.49 (ddd, 1H, H-2′, J=13.2, 6.3, 4.4), 0.92, 0.916 (2 s, 18H, tert-Bu), 0.11, 0.105 (2 s, 12H, SiCH₃). ¹³C NMR (126 MHz, CDCl₃): δ 159.1, 153.0, 152.7, 151.6, 142.2, 130.4, 129.2, 126.7, 125.6, 122.1, 117.9, 113.6, 88.1, 84.8, 71.8, 62.7, 41.5, 25.9, 25.7, 18.4, 17.9, −4.7, −4.8, −5.4, −5.5. FAB HRMS calcd for C₂₉H₄₄N₅O₄Si₂ (M⁺+H) 582.2932. found 582.2927.

Example 15 Synthesis of 3′,5′-Bis-O-(tert-butyldimethylsilyl)-O⁶-(naphth-1-yl)-2′-deoxyinosine

As described for the synthesis of 3′,5′-bis-O-(tert-butyldimethylsilyl)-O⁶-(4-nitrophenyl)-2′-deoxyinosine, this naphthyl derivative was prepared by a reaction between O⁶-(benzotriazol-1-yl)-3′,5′-bis-O-(tert-butyldimethylsilyl)-2′-deoxyinosine (26) (59.8 mg, 0.100 mmol), Cs₂CO₃ (65.2 mg, 0.200 mmol) and 1-naphthol (15.9 mg, 0.110 mmol) in dry DME (1.0 mL) at 85° C. for 2 h. Chromatographic purification (SiO₂, elution with 20% EtOAc in hexanes) afforded 49.2 mg (81% yield) of the title compound as a yellowish-white foam. R_(f) (20% EtOAc in hexanes)=0.37. ¹H NMR (500 MHz, CDCl₃): δ 8.44 (s, 1H, Ar—H), 8.41 (s, 1H, Ar—H), 7.93 (d, 1H, Ar—H, J=8.8), 7.91 (d, 1H, Ar—H, J=8.3), 7.81 (d, 1H, Ar—H, J=8.3), 7.54 (t, 1H, Ar—H, J=7.8), 7.50 (t, 1H, Ar—H, J=7.6), 7.42 (t, 1H, Ar—H, J=7.6), 7.39 (d, 1H, Ar—H, J=7.3), 6.56 (t, 1H, H-1′, J=6.4), 4.67 (m, 1H, H-3′), 4.06 (q, 1H, H-4′, J=3.4), 3.92 (dd, 1H, H-5′, J=11.2, 4.4), 3.82 (dd, 1H, H-5′, J=11.2, 2.9), 2.71 (quint, 1H, H-2′, J=6.3), 2.50 (ddd, 1H, H-2′, J=12.9, 5.9, 4.1), 0.94, 0.93 (2 s, 18H, tert-Bu), 0.12 (s, 12H, SiCH₃). ¹³C NMR (126 MHz, CDCl₃): δ 160.7, 152.7, 152.1, 148.6, 141.7, 134.9, 127.9, 127.3, 126.4, 126.2, 125.9, 125.5, 122.0, 121.9, 118.1, 88.1, 84.7, 71.9, 62.8, 41.4, 25.9, 25.7, 18.4, 18.0, −4.7, −4.8, −5.4, −5.5. FAB HRMS calcd for C₃₂H₄₇N₄O₄Si₂ (M⁺+H) 607.3136. found 607.3120.

Example 16 Synthesis of 3′,5′-Bis-O-(tert-butyldimethylsilyl)-O⁶-(fluoren-2-yl)-2′-deoxyinosine

As described for the synthesis of 3′,5′-bis-O-(tert-butyldimethylsilyl)-O⁶-(4-nitrophenyl)-2′-deoxyinosine, this fluorenyl derivative was prepared by a reaction between O⁶-(benzotriazol-1-yl)-3′,5′-bis-O-(tert-butyldimethylsilyl)-2′-deoxyinosine (26) (59.8 mg, 0.100 mmol), Cs₂CO₃ (65.2 mg, 0.200 mmol) and 2-hydroxyfluorene (20.0 mg, 0.110 mmol) in dry DME (1.0 mL) at 85° C. for 1 h. Chromatographic purification (SiO₂, elution with 20% EtOAc in hexanes) afforded 56.0 mg (87% yield) of the title compound as a clear, yellowish gum. R_(f) (20% EtOAc in hexanes)=0.31. ¹H NMR (500 MHz, CDCl₁): δ 8.52 (s, 1H, Ar—H), 8.41 (s, 1H, Ar—H), 7.83 (d, 1H, Ar—H, J=8.3), 7.77 (d, 1H, Ar—H, J=7.3), 7.53 (d, 1H, Ar—H, J=7.3), 7.45 (s, 1H, Ar—H), 7.37 (t, 1H, Ar—H, J=7.6), 7.29 (t, 1H, Ar—H, J=7.8), 6.55 (t, 1H, H-1′, J=6.4), 4.66 (m, 1H, H-3′), 4.05 (q, 1H, H-4′, J=3.4), 3.94 (s, 2H, CH₂), 3.92 (dd, 1H, H-2′, J=11.2, 4.1), 3.81 (dd, 1H, H-2′, J=11.2, 2.9), 2.67 (app quint, 1H, H-2′, J_(app)˜6.3), 2.50 (ddd, 1H, H-2′, J=13.2, 6.0, 4.3), 0.94, 0.93 (2 s, 18H, tert-Bu), 0.12 (s, 12H, SiCH₃). ¹³C NMR (126 MHz, CDCl₁): δ 160.5, 152.5, 152.1, 151.6, 144.7, 143.3, 141.6, 141.1, 139.5, 126.8, 126.5, 124.9, 122.2, 120.5, 120.47, 119.7, 118.7, 88.1, 84.7, 71.9, 62.8, 41.5, 37.0, 25.9, 25.7, 18.4, 18.0, −4.7, −4.8, −5.4, −5.5. FAB HRMS calcd for C₃₅H₄₉N₄O₄Si₂ (M⁺+H) 645.3292. found 645.3303.

Example 17 Synthesis of 3′,5′-Bis-O-(tert-butyldimethylsilyl)-O⁶-(quinolin-8-yl)-2′-deoxyinosine

As described for the synthesis of 3′,5′-bis-O-(tert-butyldimethylsilyl)-O⁶-(4-nitrophenyl)-2′-deoxyinosine, this quinolinyl derivative was prepared by a reaction between O⁶-(benzotriazol-1-yl)-3′,5′-bis-O-(tert-butyldimethylsilyl)-2′-deoxyinosine (26) (59.8 mg, 0.100 mmol), Cs₂CO₃ (65.2 mg, 0.200 mmol) and 8-hydroxyquinoline (16.0 mg, 0.110 mmo) in dry DME (1.0 mL) at 85° C. for 1 h. Chromatographic purification (SiO₂, elution with 50% EtOAc in hexanes) afforded 48.0 mg (79% yield) of the title compound as a clear gum. R_(f) (50% EtOAc in hexanes)=0.24. ¹H NMR (500 MHz, CDCl₁): δ 8.77 (dd, 1H, Ar—H, J=4.1, 1.2), 8.43 (s, 1H, Ar—H), 8.35 (s, 1H, Ar—H), 8.21 (br d, Ar—H, J=8.3), 7.79 (d, 1H, Ar—H, J=7.8), 7.66-7.60 (m, 2H, Ar—H), 7.40 (dd, 1H, Ar—H, J=8.3, 3.9), 6.54 (t, 1H, H-1′, J=6.3), 4.64 (m, 1H, H-3′), 4.04 (q, 1H, H-4′, J=3.4), 3.92 (dd, 1H, H-5′, J=11.2, 3.9), 3.81 (dd, 1H, H-5′, J=11.2, 2.9), 2.66 (app quint, 1H, H-2′, J_(app)˜6.3), 2.48 (ddd, 1H, H-2′, J=13.2, 5.9, 4.4), 0.94, 0.92 (2 s, 18H, tert-Bu), 0.123, 0.12, 0.11 (3 s, 12H, SiCH₃). ¹³C NMR (126 MHz, CDCl₃): δ 161.0, 152.6, 151.9, 150.3, 149.0, 141.6, 141.5, 135.9, 129.7, 126.4, 126.0, 121.9, 121.63, 121.6, 87.9, 84.5, 71.7, 62.7, 41.5, 26.0, 25.8, 18.5, 18.0, −4.6, −4.8, −5.3, −5.4. FAB HRMS calcd for C₃₁H₄₆N₅O₄Si₂ (M⁺+H) 608.3088. found 608.3070.

Example 18 Synthesis of O⁶-(Quinolin-8-yl)-2′,3′,5′-tris-O-(tert-butyldimethylsilyl)inosine

As described for the synthesis of 3′,5′-bis-O-(tert-butyldimethylsilyl)-O⁶-(4-nitrophenyl)-2′-deoxyinosine, this quinolinyl derivative was prepared by a reaction between O⁶-(benzotriazol-1-yl)-2′,3′,5′-tris-O-(tert-butyldimethylsilyl)inosine (27) (71.8 mg, 0.099 mmol), Cs₂CO₃ (65.2 mg, 0.200 mmol) and 8-hydroxyquinoline (16.0 mg, 0.110 mmol) in dry DME (1.0 mL) at 85° C. for 1 h. Chromatographic purification (SiO₂, elution with 50% EtOAc in hexanes) afforded 52.9 mg (72% yield) of the title compound as a white foam. R_(f) (50% EtOAc in hexanes)=0.58. ¹H NMR (500 MHz, CDCl₃): δ 8.74 (m, 1H, Ar—H), 8.48 (s, 1H, Ar—H), 8.33 (s, 1H, Ar—H), 8.20 (m, 1H, Ar—H), 7.79 (d, 1H, Ar—H, J=8.3), 7.67-7.60 (m, 2H, Ar—H), 7.39 (dd, 1H, Ar—H, J=8.5, 4.2), 6.13 (d, 1H, H-1′, J=4.4), 4.63 (t, 1H, H-2′, J=4.4), 4.37 (t, 1H, H-3′, J=4.1), 4.17 (m, 1H, H-4′), 4.07 (dd, 1H, H-5′, J=11.2, 3.4), 3.83 (dd, 1H, H-5′, J=11.2, 2.4), 0.97, 0.94, 0.84 (3S, 27H, tert-Bu), 0.17, 0.15, 0.12, 0.11, 0.0, −0.11 (6 s, 18H, SiCH₃). ¹³C NMR (126 MHz, CDCl₃): δ 161.0, 152.9, 151.9, 150.2, 149.1, 141.9, 141.5, 135.9, 129.7, 126.4, 125.9, 122.0, 121.6, 121.5, 88.7, 85.1, 76.2, 71.5, 62.3, 26.1, 25.8, 25.7, 18.6, 18.1, 17.9, −4.3, −4.7, −4.73, −4.9, −5.3, −5.4. FAB HRMS calcd for C₃₇H₆₀N₅O₅Si₃ (M⁺+H) 738.3902. found 738.3885.

Example 19 Synthesis of 6-(N-Boc-tyrosine methyl ester) purine-2′-deoxyribonucleoside conjugate

In a clean, dry reaction vial equipped with a stirring bar was placed O⁶-(benzotriazol-1-yl)-2′,3′-bis-O-(tert-butyldimethylsilyl)-2′-deoxyinosine (26) (59.8 mg, 0.100 mmol), NaHCO₃ (33.6 mg, 0.400 mmol) and Boc-L-tyrosine methyl ester (32.5 mg, 0.110 mmol). Dry DME (1.0 mL) was added and the reaction mixture was allowed to stir at 85° C. for 24 h. The reaction mixture was diluted with EtOAc and washed with water followed by brine. Chromatographic purification (SiO₂, elution with 20% acetone in hexanes) afforded 31.0 mg (41% yield) of the title compound as a clear yellowish gum. R_(f) (50% EtOAc in hexanes)=0.53. ¹H NMR (500 MHz, CDCl₃): δ 8.49 (s, 1H, Ar—H), 8.40 (s, 1H, Ar—H), 7.21 (s, 4H, Ar—H), 6.53 (t, 1H, H-1′, J=6.4), 5.03 (br d, 1H, NH, J=8.3, CD₃OD exchangeable), 4.65-4.60 (m, 2H, H-3′ and CH), 4.04 (q, 1H, H-4′, J=3.4), 3.90 (dd, 1H, H-5′, J=11.2, 3.9), 3.80 (dd, 1H, H-5′, J=11.2, 2.9), 3.73 (s, 3H, OCH₃), 3.16 (dd, 1H, PhCH_(A), J=13.9, 5.6), 3.08 (dd, 1H, PhCH_(B), J=13.9, 6.6), 2.64 (app quint, 1H, H-2′, J_(app)˜6.3), 2.48 (ddd, 1H, H-2′, J=13.2, 5.9, 3.9), 1.43 (s, 9H, tert-BuO), 0.93, 0.92 (2 s, 18H, tert-BuSi), 0.11 (s, 12H, SiCH₃). ¹³C NMR (126 MHz, CDCl₃): δ 172.3, 160.1, 155.1, 152.4, 151.9, 151.4, 141.7, 133.5, 130.4, 122.0, 121.9, 88.0, 84.6, 80.0, 71.74, 71.72, 62.7, 54.3, 52.3, 41.5, 37.8, 28.3, 26.0, 25.7, 18.4, 18.0, −4.7, −4.8, −5.4, −5.5. FAB HRMS calcd for C₃₇H₆₀N₅O₈Si₂ (M⁺+H) 758.3980. found 758.4008.

Example 20 Synthesis of 1,4-Bis-[O⁶-(3′,5′-bis-O-tert-butyldimethylsilyl)-2′-deoxyinosyl]phenyl ether

As described for the synthesis of 3′,5′-bis-O-(tert-butyldimethylsilyl)-O⁶-(4-nitrophenyl)-2′-deoxyinosine, this dimeric product was prepared by a reaction between O⁶-(benzotriazol-1-yl)-2′,3′-bis-O-(tert-butyldimethylsilyl)-2′-deoxyinosine (26) (59.8 mg, 0.100 mmol), Cs₂CO₃ (65.2 mg, 0.200 mmol) and hydroquinone (4.4 mg, 0.040 mmol) in dry DME (1.0 mL) at 85° C. for 3 h. Purification by preparative thin layer chromatography (SiO₂, elution with 50% EtOAc in hexanes) afforded 35.0 mg (68% yield) of the title compound as a clear, yellowish gum. R_(f) (3% MeOH in CH₂Cl₂)=0.14. ¹H NMR (500 MHz, CDCl₃): δ 8.52 (s, 2H, Ar—H), 8.40 (s, 2H, Ar—H), 7.37 (s, 4H, Ar—H), 6.54 (t, 2H, H-1′, J=6.3), 4.65 (m, 2H, H-3′), 4.05 (q, 2H, H-4′, J=3.4), 3.91 (dd, 2H, H-5′, J=11.2, 3.9), 3.80 (dd, 2H, H-5′, J=11.2, 2.9), 2.66 (app quint, 2H, H-2′, J_(app)˜6.3), 2.49 (ddd, 2H, H-2′, J=13.2, 5.9, 4.4), 0.93, 0.92 (2 s, 36H, tert-Bu), 0.11 (s, 24H, SiCH₃). ¹³C NMR (126 MHz, CDCl₃): δ 160.0, 152.6, 151.9, 149.7, 141.6, 122.7, 122.2, 88.1, 84.7, 71.9, 62.8, 41.4, 25.9, 25.7, 18.4, 17.9, −4.7, −4.8, −5.4, −5.5. FAB HRMS calcd for C₅₀H₈₄N₈O₈Si₄ (M⁺+H) 1035.5411. found 1035.5377.

Example 21 Synthesis of 6-(Morpholin-4-yl)-9-[2-deoxy-3,5-bis-O-(tert-butyldimethylsilyl)-β-D-erythro-pentofuranosyl]purine

In a clean, dry reaction vial equipped with a stirring bar were placed O⁶-(benzotriazol-1-yl)-3′,5′-bis-O-(tert-butyldimethylsilyl)-2′-deoxyinosine (26) (59.8 mg, 0.100 mmol), Cs₂CO₃ (65.2 mg, 0.200 mmol) and dry DME (1.0 mL). Morpholine (17.5 μL, 0.200 mmol) was added, the reaction mixture was flushed with N₂, and the mixture was allowed to stir at room temperature for 1 h. The reaction mixture was concentrated and the residue was dissolved in EtOAc. The mixture was washed with 10% aq citric acid, sat aq NaHCO₃ and brine. The organic layer was dried over Na₂SO₄ and evaporated to dryness. No additional purification was needed and 43 mg (78% yield) of the title compound was obtained. R_(f) (3% MeOH in CH₂Cl₂)=0.18. ¹H NMR (500 MHz, CDCl₃): δ 8.34 (s, 1H, Ar—H), 8.02 (s, 1H, Ar—H), 6.46 (t, 1H, H-1′, J=6.6), 4.59 (m, 1H, H-3′), 4.30 (br s, 4H, 2CH₂), 4.01 (app q, 1H, H-4′, J_(app)˜3.4), 3.85-3.82 (m, 5H, H-5′ and 2CH₂), 3.76 (dd, 1H, H-5′, J=11.0, 3.2), 2.59 (app quint, 1H, H-2′, J_(app)˜6.5), 2.42 (ddd, 1H, H-2′, J=13.2, 5.9, 3.9), 0.91 (s, 18H, tert-Bu), 0.09, 0.08, 0.076 (3 s, 12H, SiCH₃). ¹³C NMR (126 MHz, CDCl₃): δ 153.9, 152.3, 150.6, 136.8, 120.4, 87.8, 84.1, 72.0, 67.0, 62.8, 45.6, 41.1, 26.0, 25.7, 18.4, 18.0, −4.7, −4.8, −5.4, −5.5. FAB HRMS calcd for C₂₆H₄₈N₅O₄Si₂ (M⁺+H) 550.3245. found 550.3222.

Example 22 Synthesis of 6-(Morpholin-4-yl)-9-[2,3,5-tris-O-(tert-butyldimethylsilyl)-β-D-ribofuranosyl]purine

As described for the synthesis of 6-(morpholin-1-yl)-9-[2-deoxy-3,5-bis-O-(tert-butyldimethylsilyl)-β-D-erythro-pentofuranosyl]-purine, this morpholino derivative was prepared by a reaction between O⁶-(benzotriazol-1-yl)-2′,3′,5′-tris-O-(tert-butyldimethylsilyl)-inosine (27) (71.8 mg, 0.099 mmol), and morpholine (17.5 μL, 0.200 mmol) in the presence of Cs₂CO₃ (65.2 mg, 0.200 mmol) in dry DME (1.0 mL) at room temperature over 1 h. No additional purification was needed and 57.5 mg (85% yield) of the title compound was obtained. R_(f) (3% MeOH in CH₂Cl₂)=0.68. ¹H NMR (500 MHz, CDCl₃): δ 8.33 (s, 1H, Ar—H), 8.03 (s, 1H, Ar—H), 6.03 (d, 1H, H-1′, J=5.4), 4.72 (t, 1H, H-2′, J=4.9), 4.32-4.29 (br m, 5H, H-3′ and 2CH₂), 4.11 (q, 1H, H-4′, J=3.6), 4.02 (dd, 1H, H-5′, J=11.2, 4.4), 3.83 (t, 4H, 2CH₂, J=4.6), 3.77 (dd, 1H, H-5′, J=11.2, 3.2), 0.95, 0.93, 0.80 (3 s, 27H, tert-Bu), 0.124, 0.12, 0.104, 0.10, −0.05, −0.22 (6 s, 18H, SiCH₃). ¹³C NMR (126 MHz, CDCl₃): δ 153.9, 152.2, 150.9, 137.7, 120.5, 88.1, 85.4, 75.4, 72.1, 67.0, 62.6, 45.6, 26.1, 25.8, 25.7, 18.5, 18.1, 17.9, −4.4, −4.7, −5.0, −5.4, −5.41.

Example 23 Synthesis of 9-(2-Deoxy-β-D-erythro-pentofuranosyl)-6-(morpholin-4-yl)purine

As described for the synthesis of 6-(morpholin-1-yl)-9-[2-deoxy-3,5-bis-O-(tert-butyldimethylsilyl)-β-D-erythro-pentofuranosyl]purine, this morpholino derivative was prepared by a reaction between O⁶-(benzotriazol-1-yl)-2′-deoxyinosine (28) (36.9 mg, 0.100 mmol), and morpholine (17.5 μL, 0.200 mmol) in the presence of Cs₂CO₃ (65.2 mg, 0.200 mmol) in dry DME (1.0 mL) at room temperature over 1 h. Chromatographic purification (SiO₂, elution with 5% MeOH in CH₂Cl₂) afforded 16.6 mg (52% yield) of the title compound as a clear gum. R_(f) (10% MeOH in CH₂Cl₂)=0.34. ¹H NMR (500 MHz, CDCl₃): δ 8.26 (s, 1H, Ar—H), 7.77 (s, 1H, Ar—H), 6.88 (br, 1H, OH, CD₃OD exchangeable), 6.30 (dd, 1H, H-1′, J=9.8, 5.4), 4.77 (d, 1H, H-3′, J=4.8), 4.30 (br, 4H, 2CH₂), 4.21 (br s, 1H, H-4′), 3.96 (dd, 1H, H-5′, J=12.7, 1.2), 3.81 (t, 4H, 2CH₂, J=4.9), 3.77 (br d, 1H, H-5′, J=13.2), 3.10 (ddd, 1H, H-2′, J=13.7, 9.3, 4.9), 2.65 (br, 1H, OH, CD₃OD exchangeable), 2.26 (dd, 1H, H-2′, J=13.7, 5.6). ¹³C NMR (126 MHz, CDCl₃): δ 154.1, 151.6, 149.4, 138.3, 121.7, 89.7, 87.8, 73.6, 67.0, 63.5, 45.6, 40.5.

Example 24 Synthesis of 6-(Morpholin-4-yl)-9-(β-D-ribofuranosyl)purine

As described for the synthesis of 3′,5′-bis-O-(tert-butyl-dimethylsilyl)-O⁶-methyl-2′-deoxyinosine, this morpholino derivative was prepared by a reaction between O⁶-(benzotriazol-1-yl)inosine (29) (38.5 mg, 0.100 mmol), Cs₂CO₃ (65.2 mg, 0.200 mmol) and morpholine (17.5 μL, 0.200 mmol) in dry DME (1.0 mL). Chromatographic purification (SiO₂, elution with 10% MeOH in CH₂Cl₂) gave a slightly impure material (˜77% yield). Recrystallization from MeOH afforded 19.6 mg (58% yield) of the title compound as a white solid. R_(f) (10% MeOH in CH₂Cl₂)=0.27. ¹H NMR (500 MHz, DMSO-d₆): δ 8.47 (s, 1H, Ar—H), 8.30 (s, 1H, Ar—H), 5.96 (d, 1H, H-1′, J=5.9), 5.51 (d, 1H, OH, J=6.4, D₂O exchangeable), 5.35 (dd, 1H, OH-5′, J=6.8, 4.9, D₂O exchangeable), 5.24 (d, 1H, OH, H=4.9, D₂O exchangeable), 4.61 (q, 1H, H-2′, J=5.6), 4.25 (br, 4H, 2CH₂), 4.18 (app q, 1H, H-3′, J_(app)˜4.4), 4.00 (q, 1H, H-4′, J=3.4), 3.75 (t, 4H, 2CH₂, J=4.9), 3.71 (dt, 1H, H-5′, J=11.7, 4.4), 3.59 (ddd, 1H, H-5′, J=11.7, 6.8, 3.9). ¹³C NMR (126 MHz, DMSO-d₆): δ 154.0, 152.5, 151.0, 139.7, 120.4, 88.5, 86.4, 74.2, 71.2, 66.9, 62.2, 46.0.

Example 25 Synthesis of 6-(Imidazol-1-yl)-9-[2-deoxy-3,5-bis-O-(tert-butyldimethylsilyl)-β-D-erythro-pentofuranosyl]purine

In a clean, dry reaction vial equipped with a stirring bar were placed O⁶-(benzotriazol-1-yl)-2′,3′-bis-O-(tert-butyldimethylsilyl)-2′-deoxyinosine (26) (59.8 mg, 0.100 mmol), Cs₂CO₃ (65.2 mg, 0.200 mmol) and imidazole (13.6 mg, 0.200 mmol). Dry DME (1.0 mL) was added and the reaction mixture was flushed with N₂ and the mixture was allowed to stir at 85° C. for 4 h. The reaction mixture was concentrated and the residue was dissolved in EtOAc. The mixture was washed with water, dried over Na₂SO₄, and evaporated to dryness. Chromatographic purification (SiO₂, elution with 50% EtOAc in hexanes) afforded 32.0 mg (60% yield) of the title compound as a clear gum. R_(f) (20% EtOAc in hexanes)=0.07. ¹H NMR (500 MHz, CDCl₃): δ 9.19 (s, 1H, Ar—H), 8.77 (s, 1H, Ar—H), 8.48 (s, 1H, Ar—H), 8.40 (s, 1H, Ar—H), 7.25 (s, 1H, Ar—H), 6.56 (t, 1H, H-1′, J=6.3), 4.64 (app q, 1H, H-3′, J_(app)˜4.2), 4.06 (m, 1H, H-4′), 3.90 (dd, 1H, J=11.2, 3.9), 3.80 (dd, 1H, H-5′, J=11.2, 2.9), 2.65 (app quint, 1H, H-2′, J_(app)˜6.3), 2.51 (m, 1H, H-2′), 0.92, 0.915 (2 s, 18H, tert-Bu), 0.11, 0.10 (2 s, 12H, SiCH₃). ¹³C NMR (126 MHz, CDCl₃): δ 153.0, 152.1, 145.6, 143.0, 137.7, 130.6, 122.9, 117.3, 88.1, 84.7, 71.7, 62.6, 41.5, 25.9, 25.7, 18.4, 18.0, −4.7, −4.8, −5.4, −5.5.

Example 26 Synthesis of 3′,5′-Bis-O-(tert-butyldimethylsilyl)-N⁶-benzyl-2′-deoxyadenosine

As described for the synthesis of 6-(morpholin-1-yl)-9-[2-deoxy-3,5-bis-O-(tert-butyldimethylsilyl)-β-D-erythro-pentofuranosyl]purine, the benzyl derivative was prepared by a reaction between O⁶-(benzotriazol-1-yl)-3′,5′-bis-O-(tert-butyldimethylsilyl)-2′-deoxyinosine (26) (59.8 mg, 0.100 mmol) and benzylamine (21.8 μL, 0.200 mmol) in the presence of Cs₂CO₃ (65.2 mg, 0.200 mmol) in dry DME (1.0 mL) at room temperature over 6 h. Chromatographic purification (SiO₂, elution with 20% EtOAc in hexanes followed by 50% EtOAc in hexanes) afforded 35.0 mg (84% yield) of the title compound as a clear gum. R_(f) (3% MeOH in CH₂Cl₂)=0.07. ¹H NMR (500 MHz, CDCl₃): δ 8.41 (s, 1H, Ar—H), 8.11 (s, 1H, Ar—H), 7.38 (d, 2H, Ar—H, J=7.5), 7.33 (t, 2H, Ar—H, J=7.6), 7.28 (m, 1H, Ar—H), 6.45 (t, 1H, H-1′, J=6.6), 5.98 (br s, 1H, NH), 4.87 (br s, 2H, CH₂), 4.61 (m, 1, H-3′), 4.01 (q, 1H, H-4′, J=3.4), 3.87 (dd, 1H, H-5′, J=5.9, 4.4), 3.77 (dd, 1H, H-5′, J=5.9, 4.4), 2.64 (quint, 1H, H-2′. J=6.3), 2.43 (ddd, 1H, H-2′, J=13.2, 6.4, 3.9), 0.91 (s, 18H, tert-Bu), 0.10, 0.09, 0.08 (3 s, 12H, SiCH₃). ¹³C NMR (126 MHz, CDCl₃): δ 154.6, 153.1, 138.4, 128.6, 127.8, 127.5, 120.2, 87.8, 84.3, 71.2, 62.8, 41.2, 25.9, 25.8, 18.4, 18.0, −4.7, −4.8, −5.4, −5.5. FAB HRMS calcd for C₂₉H₄₈N₅O₃Si₂ (M⁺+H) 570.3296. found 570.3279.

Example 27 Synthesis of 2′,3′,5′Tris-O-(tert-butyldimethylsilyl)-N⁶-benzyladenosine

As described for the synthesis of 6-(morpholin-4-yl)-9-[2-deoxy-3,5-bis-O-(tert-butyldimethylsilyl)-β-D-erythro-pentofuranosyl]purine, this benzyl derivative was prepared by a reaction between O⁶-(benzotriazol-1-yl)-2′,3′,5′-tris-O-(tert-butyldimethylsilyl)inosine (27) (71.8 mg, 0.099 mmol) and benzylamine (21.8 μL, 0.200 mmol) in the presence of Cs₂CO₃ (65.2 mg, 0.200 mmol) in dry DME (1.0 mL) at room temperature over 7 h. Chromatographic purification (SiO₂, elution with 3% EtOAc in hexanes followed by 20% EtOAc in hexanes) afforded 61.0 mg (87% yield) of the title compound as a clear gum. R_(f) (20% EtOAc in hexanes)=0.39. ¹H NMR (500 MHz, CDCl₃): δ 8.40 (s, 1H, Ar—H), 8.09 (s, 1H, Ar—H), 7.38 (d, 2H, Ar—H, J=7.3), 7.34 (t, 2H, Ar—H, J˜7.3), 7.28 (app t, 1H, Ar—H, J_(app)˜8.5), 6.02 (d, 1H, H-1′, J=5.4), 5.95 (br s, 1H, NH), 4.86 (br s, 2H, CH₂), 4.70 (t, 1H, H-2′, J=4.9), 4.32 (t, 1H, H-3′, J=3.9), 4.12 (q, 1H, H-4′, J=3.4), 4.03 (dd, 1H, H-5′, J=11.2, 4.1), 3.78 (dd, 1H, H-5′, J=11.2, 2.9), 0.95, 0.93, 0.80 (3 s, 27H, tert-Bu), 0.13, 0.12, 0.11, 0.10, −0.04, −0.22 (6 s, 18H, SiCH₃). ¹³C NMR (126 MHz, CDCl₃): δ 154.7, 153.0, 149.4, 139.1, 138.6, 128.6, 127.7, 127.4, 120.4, 88.4, 85.4, 75.6, 72.1, 62.6, 44.8, 26.0, 25.8, 25.7, 18.4, 18.0, 17.8, −4.4, −4.7, −5.1, −5.4.

Example 28 Synthesis of 6-Thiobenzyl-9-[2-deoxy-3,5-bis-O-(tert-butyldimethylsilyl)-β-D-etythro-pentofuranosyl]purine

As described for the synthesis of 3′,5′-bis-O-(tert-butyldimethylsilyl)-O⁶-(4-nitrophenyl)-2′-deoxyinosine, this thiobenzyl derivative was prepared by a reaction between O⁶-(benzotriazol-1-yl)-3′,5′-bis-O-(tert-butyldimethylsilyl)-2′-deoxyinosine (26) (59.8 mg, 0.100 mmol) and benzylmercaptan (23.5 μL, 0.200 mmol) in the presence of Cs₂CO₃ (65.2 mg, 0.200 mmol) in dry DME (1.0 mL) at room temperature over 1 h. Chromatographic purification (SiO₂, elution with CH₂Cl₂ followed by 20% EtOAc in hexanes) afforded 50.1 mg (85% yield) of the title compound as a clear, yellowish gum. R_(f) (20% EtOAc in hexanes)=0.40. ¹H NMR (500 MHz, CDCl₃): δ 8.73 (s, 1H, Ar—H), 8.27 (s, 1H, Ar—H), 7.47 (d, 2H, Ar—H, J=7.6), 7.31-7.22 (m, 3H, Ar—H), 6.49 (t, 1H, H-1′, J=6.4), 4.67 (AB_(quartet), 2H, CH₂, J=13.6), 4.62 (m, 1H, H-3′), 4.03 (app q, 1H, H-4′, J˜3.5), 3.87 (dd, 1H, H-5′, J=11.3, 4.3), 3.77 (dd, 1H, H-5′, J=11.3, 3.2), 2.65 (m, 1H, H-2′), 2.44 (ddd, 1H, H-2′, J=13.1, 6.1, 3.7), 0.92, 0.91, 0.90 (3 s, 18H, tert-Bu), 0.11, 0.08, 0.079 (3 s, 12H, SiCH₃). ¹³C NMR (126 MHz, CDCl₃): δ 160.6, 151.7, 148.1, 141.2, 137.5, 131.7, 129.1, 128.5, 127.2, 88.0, 84.5, 72.0, 62.8, 41.3, 32.8, 26.0, 25.8, 18.4, 18.0, −4.7, −4.8, −5.4, −5.5. FAB HRMS calcd for C₂₉H₄₇N₄O₃SSi₂ (M⁺+H) 587.2907. found 587.2906.

Example 29 Synthesis of 6-Thiobenzyl-9-[2,3,5-tris-O-(tert-butyldimethylsilyl)-β-D-erythro-pentofuranosyl]purine

In a clean, dry reaction vial equipped with a stirring bar was placed O⁶-(benzotriazol-1-yl)-2′,3′,5′-tris-O-(tert-butyldimethylsilyl)inosine (27) (72.8 mg, 0.100 mmol), Cs₂CO₃ (65.2 mg, 0.200 mmol) and benzylmercaptan (23.5 μL, 0.200 mmol). Dry DME (1.0 mL) was added and the reaction mixture was allowed to stir at room temperature for 7 h and then concentrated. Chromatographic purification (SiO₂, elution with 5% EtOAc in hexanes followed by 20% EtOAc in hexanes) afforded 66.5 mg (93% yield) of the title compound as a clear gum. R_(f) (20% EtOAc in hexanes)=0.59. ¹H NMR (500 MHz, CDCl₃): δ 8.73 (s, 1H, Ar—H), 8.31 (s, 1H, Ar—H), 7.48-7.46 (m, 2H, Ar—H), 7.32-7.23 (m, 3H, Ar—H), 6.08 (d, 1H, H-1′, J=5.2), 4.67 (AB_(quartet), 2H, CH₂, J=13.4), 4.66 (app t, 1H), H-2′, J_(app)˜4.8), 4.33 (t, 1H, H-3′, J=4.0), 4.14 (q, 1H, H-4′, J=3.5), 4.02 (dd, 1H, H-5′, J=11.3, 4.0), 3.79 (dd, 1H, H-5′, J=11.3, 2.9), 0.95, 0.945, 0.94, 0.80 (4 s, 27H, tert, Bu), 0.14, 0.13, 0.11, 0.105, −0.03, −0.23 (6 s, 18H, SiCH₃). ¹³C NMR (126 MHz, CDCl₃): δ 160.6, 151.8, 148.4, 141.7, 137.5, 131.7, 129.1, 128.5, 127.2, 88.4, 85.5, 75.9, 71.9, 62.5, 32.9, 26.1, 25.8, 25.7, 18.5, 18.1, 17.8, −4.4, −4.7, −4.71, −5.0, −5.4. FAB HRMS calcd for C₃₅H₆₁N₄O₄SSi₃ (M⁺+H) 717.3721. found 717.3734.

Example 30 Synthesis of N¹-[6-[9-(2-deoxy-3,5-bis-O-(tert-butyldimethylsilyl)-β-D-erythro-pentofuranosyl)]purinyl]-3′,5′-bis-O-(tert-butyldimethylsilyl)-2′-deoxyinosine

As described for the synthesis of 3′,5′-bis-O-(tert-butyldimethylsilyl)-O⁶-phenyl-2′-deoxyinosine, this unsymmetrical dimer was prepared by a reaction between O⁶-(benzotriazol-1-yl)-3′,5′-bis-O-(tert-butyldimethylsilyl)-2′-deoxyinosine (26) (20.0 mg, 0.0334 mmol) and 3′,5′-bis-O-(tert-butyldimethylsilyl)-2′-deoxyinosine (22) (16.1 mg, 0.0334) in the presence of K₃PO₄ (10.6 mg, 0.050 mmol) in dry toluene (0.33 mL) at 105° C. over 3 h. Chromatographic purification (SiO₂, elution with 20% EtOAc in hexanes followed by 5% MeOH in CH₂Cl₂) afforded 28.9 mg, 92% yield of the title compound as a clear, yellowish gum. R_(f) (3% MeOH in CH₂Cl₂)=0.09. ¹H NMR (500 MHz, CDCl₃): δ 8.99 (s, 1H, Ar—H), 8.50 (s, 1H, Ar—H), 8.25 (s, 1H, Ar—H), 8.15 (s, 1H, Ar—H), 6.57 (t, 1H, H-1′, J=6.4), 6.43 (app t, 1H, H-1′, J_(app)˜6.3), 4.65-4.60 (m, 2H, 2H-3′), 4.06 (q, 1H, H-4′, J=3.4), 4.03 (q, 1H, H-4′, J=3.4), 3.88 (dd, 1H, H-5′, J=11.2, 3.9), 3.86 (dd, 1H, H-5′, J=10.5, 4.2), 3.79 (dd, 2H, 2H-5′, J=11.2, 2.9), 2.68 (app quint, 1H, H-2′, J_(app)˜6.3), 2.57 (app quint, 1H, H-2′, J_(app)˜6.3), 2.50 (ddd, 1H, H-2′, J=13.2, 6.3, 3.9), 2.45 (ddd, 1H, H-2′, J=13.2, 5.9, 3.9), 0.93, 0.92, 0.918, 0.90 (4 s, 36H, tert-Bu), 0.13, 0.12, 0.11, 0.10, 0.09, 0.08, (6 s, 24H, SiCH₃). ¹³C NMR (126 MHz, CDCl₃): δ 155.1, 153.3, 152.2, 147.8, 146.9, 145.9, 144.6, 138.4, 129.9, 124.9, 88.2, 88.1, 84.9, 84.6, 71.9, 71.8, 62.7, 41.8, 41.4, 26.0, 25.7, 18.4, 18.0, −4.7, −4.8, −5.4, −5.5. FAB HRMS calcd for C₄₄H₇₉N₈O₇Si₄ (M⁺+H) 943.5149. found 943.5159.

Example 31 Synthesis of O⁶-(Benzotriazol-1-yl)-5′-O-(4,4′-dimethoxytrityl)-2′-deoxyinosine

In a 100 mL round-bottomed flask equipped with a stirring bar were placed 5′-O-(4,4′-dimethoxytrityl)-2′-deoxyinosine²⁶ (0.7 g, 1.262 mmol), BOP (1.117 g, 2.524 mmol), DIPEA (0.44 mL, 2.524 mmol) and dry THF (50.0 mL). The reaction mixture was allowed to stir at room temperature under a N₂ balloon for 40 h. The reaction mixture was evaporated, diluted with EtOAc (200 mL) and washed with brine. The organic layer was dried over Na₂SO₄ and concentrated. Chromatographic purification (SiO₂, packed with 1% DIPEA in EtOAc and elution with EtOAc) afforded 0.718 g (85% yield) of the title compound as a white foam. R_(f) (EtOAc)=0.31. ¹H NMR (500 MHz, CDCl₃): δ 8.31 (s, 1H, Ar—H), 8.28 (s, 1H, Ar—H), 8.13 (d, 1H, Ar—H, J=8.2), 7.55-7.45 (m, 3H, Ar—H), 7.38 (d, 2H, Ar—H, J=7.3), 7.29-7.19 (m, 7H, Ar—H), 6.80 (d, 4H, Ar—H, J=8.9), 6.52 (t, 1H, H-1′, J=6.4), 4.73 (br m, 1H, H-3′), 4.20 (q, 1H, H-4′, J=4.2), 3.77 (s, 6H, OCH₃), 3.45 (dd of AB_(quartet), 1H, H-5′, J=10.4, 4.6), 3.40 (dd of AB_(quartet), 1H, H-5′, J=10.4, 5.0), 2.87 (app quint, 1H, H-2′, J_(app)˜6.6), 2.62 (ddd, 1H, H-2′, J=13.4, 6.2, 4.3), 2.39 (d, 1H, 3′-OH, J=3.1). ¹³C NMR (126 MHz, CDCl₃): δ 159.1, 158.6, 153.5, 151.4, 144.4, 143.5, 135.5, 135.4, 130.0, 128.9, 128.8, 128.0, 127.9, 127.1, 124.8, 120.6, 120.1, 113.2, 108.7, 86.8, 86.3, 85.0, 72.6, 63.5, 55.2, 40.3. FAB HRMS calcd for C₃₇H₃₄N₇O₆ (M⁺+H) 672.2571. found 672.2583.

Example 32 Synthesis of O⁶-(Benzotriazol-1-yl)-3′-O—[(N,N-diisopropylamino)(β-cyanoethoxy)phosphinyl]-5′-O-(4,4′-dimethoxytrityl)-2′-deoxyinosine

In a clean, dry vial equipped with a stirring bar was placed O⁶-(benzotriazol-1-yl)-5′-O-(4,4′-dimethoxytrityl)-2′-deoxyinosine (0.030 g, 0.0447 mmol) and the vial was transferred to a glove bag maintained under N₂. CH₂Cl₂ (0.5 mL), DIPEA (19.5 μL, 0.112 mmol) and 2-cyanoethyl diisopropylchlorophosphoramidite (19.9 μL, 0.0894 mmol) were added. The mixture was removed from the glove bag and allowed to stir at room temperature for 1 h under a N₂ atmosphere. The reaction mixture was diluted with CH₂Cl₂ and washed with saturated NaHCO₃ followed by brine. The organic layer was dried over Na₂SO₄ and concentrated. Chromatographic purification (SiO₂ packed with 50/50/1 EtOAc/hexanes/DIPEA and eluted with 50% EtOAc in hexanes) afforded 18.4 mg (47% yield) of the title compound as a white, foamy solid. R_(f) (50/50/1 EtOAc/hexanes/DIPEA)=0.51 and 0.45 for the two phosphoramidite diastereomers. ³¹P NMR (202 MHz, CDCl₃): δ 150.08 and 150.00.

Example 33 Synthesis of O⁴-(Benzotriazol-1-yl)-3′,5′-bis-O-(tert-butyldimethylsilyl)thymidine

As described for the synthesis of 26, this compound was prepared by a reaction between 3′,5′-bis-O-(tert-butyldimethylsilyl)thymidine (0.235 g, 0.998 mmol), BOP (0.443 g, 0.998 mmol) and NaH (47.9 mg, 1.997 mmol) in dry THF (5 mL). Chromatographic purification (SiO₂, elution with 3% MeOH in CH₂Cl₂) yielded 197 mg (67% yield along with 29% of starting material) of the title compound as a clear gum. R_(f) (3% MeOH in CH₂Cl₂)=0.44. ¹H NMR (500 MHz, CDCl₃): δ 8.16 (s, 1H, vinyl H), 7.54-7.40 (m, 4H, Ar—H), 6.19 (t, H-1′, J=6.1), 4.39-4.36 (m, 1H, H-3′), 4.01-3.99 (br m, 1H, H-4′), 3.96 (dd, 1H, H-5′, J=11.7, 2.4), 3.80 (dd, 1H, H-5′, J=11.7, 2.4), 2.51 (ddd, 1H, 1H, H-2′, J=13.2, 6.2, 3.9), 4.04 (app q, 1H, H-2′, J_(app)=˜6.4), 0.96, 0.88 (2 s, 18H, tert-Bu), 0.16, 0.14, 0.07 (3 s, 12H, SiCH₃).

Example 34 Synthesis of polystyrene-supported O⁶-(benzotriazol-1-yl)-3′,5′-bis-O-(tert-butyldimethylsilyl)-2′-deoxyinosine (30)

Into a 50 mL round-bottomed flask equipped with a stirring bar were placed I₂ (0.914 g, 3.60 mmol) and dry CH₂Cl₂ (30 mL). HMPT (0.65 mL, 3.60 mmol) was added slowly and the mixture was stirred at room temperature for 10 min. DIPEA (1.67 mL, 9.60 mmol) and 3′,5′-bis-O-(tert-butyldimethylsilyl)-2′-deoxyinosine (22) (1.154 g, 2.40 mmol) were added and the mixture was allowed to stir at room temperature for 1.5 h. PS-HOBt (3.672 g, 3.60 mmol) was added to this solution and the resin suspension was allowed to stir at room temperature for 21 h. The resin was filtered, washed sequentially with CH₂Cl₂, 5% MeOH in CH₂Cl₂, CH₂Cl₂ and Et₂O and then dried under vacuum. The polystyrene-supported O⁶-(benzotriazol-1-yl)-3′,5′-bis-O-(tert-butyldimethylsilyl)-2′-deoxyinosine (30) was obtained as pale brownish resin (4.650 g).

Example 35 Synthesis of polystyrene-supported O⁶-(benzotriazol-1-yl)-2′,3′,5′-tris-O-(tert-butyldimethylsilyl)inosine (31)

As described for the synthesis of 30, 31 was prepared by a reaction between I₂ (0.571 g, 2.25 mmol), HMPT (0.41 mL, 2.25 mmol), DIPEA (1.05 mL, 6.00 mmol) and 2′,3′,5′-tris-O-(tert-butyldimethylsilyl)inosine (23) (0.917 g, 1.50 mmol) and PS-HOBt (2.206 g, 2.25 mmol) in dry CH₂Cl₂ (20 mL). The polystyrene-supported O⁶-(benzotriazol-1-yl)-2′,3′,5′-tris-O-(tert-butyldimethylsilyl)inosine (31) was obtained as yellow resin (2.793 g).

Example 36 Synthesis of a DNA Building Block and Site-Specific DNA Modification

As shown in the reaction scheme above, reaction of the known 5′-O-DMT-2′-deoxyinosine 32 with 2 mol equivalents each of BOP and (iso-Pr)₂NEt at room temperature over 40 hours led to the O⁶-(benzotriazol-1-yl)-5′-O-DMT-2′-deoxyinosine 33 in 85% isolated yield. Finally, conversion of 33 to the phosphoramidite 34 was accomplished by conventional methods (47% yield).

Compound 34 was incorporated into the 11-mer oligonucleotide 35 using standard phosphoramidite chemistry. The support-bound reactive DNA 35 was then exposed to a DMF solution of morpholine for 24 hours at room temperature. The DNA was subjected to standard cleavage from the support and deprotection followed by LC/MS analysis. This analysis showed the presence of the desired morpholine modified DNA oligomer 36 (mass 3665.7) (SEQ ID NO: 1 and the T₁₀ oligomer (mass 2980.3) in a nearly 1:1 ratio indicating the coupling efficiency of 35 to be ˜50%. DNA assembly was performed with only 6 mg of compound 35. Coupling efficiency can be substantially improved by altering factors such as increased concentrations of compound 35 and longer coupling times. Only the desired morpholine modified oligomer 36 was obtained by the reaction. The ammonia displacement product was not observed. The ammonia displacement product would have been formed in the ammonia cleavage step had incomplete displacement by morpholine occurred. Accordingly, the DNA containing the reactive nucleoside underwent conversion in essentially quantitative yield to compound 35. The results from these experiments indicate the suitability of phorphoramidite 34 for DNA incorporation and for displacement reactions post-assembly.

Example 37 Synthesis of 1,N⁶-ethano- and 1,N⁶-propano-2′-deoxyadenosine analogues

In reaction scheme above, compound 26 is a precursor to 1,N⁶-ethano-2′-deoxyadenosine and 1,N⁶-propano-2′-deoxyadenosine. The synthetic methodology is adequately flexible to accommodate chain length variation.

The O⁶-(benzotriazol-1-yl)inosine nucleosides undergo reactions with both alcohols and amines, however, the former requires the use of Cs₂CO₃. Using this difference in reactivity, compound 26 was allowed to react with either 2-aminoethanol or with 3-amino-1-propanol in 1,2-dimethoxyethane (DME) at room temperature. The amination products 37 and 38 were obtained in 95% and 96% yields, respectively. Conversion of the terminal hydroxyl group in 37 and 38 to an iodide resulted in spontaneous cyclization to 39 and 40. For this cyclization two methods were evaluated; (PhO)₃P³⁰MeI⁻/Et₃N in DMF and PPh₃/I₂/DIPEA/CH₂Cl₂. The results from these experiments are shown in Table 4. Both sets of reagents produced the desired cyclization in reasonable, but slightly differing yields.

TABLE 4 Conditions tested for the cyclization of 6 and 7 Entry Substrate Cyclization conditions Product, yield^(a) 1 37, n = 1 (PhO)₃P⁺MeI⁻, Et₃N, DMF, rt, 3 h 39, 51% 2 37, n = 1 PPh₃, I₂, DIPEA, CH₂Cl₂, 8 h 39, 61% 3 38, n = 2 (PhO)₃P⁺MeI⁻, Et₃N, DMF, rt, 3 h 40, 78% 4 38, n = 2 PPh₃, I₂, DIPEA, CH₂Cl₂, 8 h 40, 62% ^(a)Yield of isolated and purified product.

INCORPORATION OF SEQUENCE LISTING

Incorporated herein by reference in its entirety is the Sequence Listing for the application. The Sequence Listing is disclosed on a computer-readable ASCII text file titled, “Sequence Listing”, created on Nov. 20, 2012. The Sequence Listing.txt file is 1 kb in size. 

We claim:
 1. A compound having the formula ZOR, wherein: Z represents:

R represents:

R¹ and R² independently represent CR³ or N; R⁴, R⁵, R⁶, R⁷, R⁸, R⁹, R¹⁰, R¹¹, R¹², and R¹³ represent, independently, N or CQ, with the proviso that no more than three of R⁴, R⁵, R⁶, and R⁷ represents N; X represents R¹⁴, —OR¹⁵, SR¹⁵, —N(R¹⁴)₂, R¹⁴C(O)—, nitro, or halo; Q and R³, independently of each other, and independently at each position, represent R¹⁴, —OR¹⁵, —SR¹⁵, —N(R¹⁴)₂, R¹⁴C(O)—, nitro, or halo; Y represents R¹⁴ or a saccharide moiety; R¹⁴ independently represents H, an alkyl group, a carbocyclic aryl group, or a heterocyclic group; and R¹⁵ independently represents R¹⁴ or a protecting group; wherein: alkyl groups are branched or unbranched and have 1-18 carbon atoms; alkyl groups are optionally substituted with halo groups; carbocyclic aryl groups have a total of 6-20 carbon atoms, including carbon atoms of substituents; heterocyclic aryl groups have a total of 5-20 carbon atoms, including carbon atoms of substituents; and carbocyclic aryl groups and heterocyclic aryl groups are unsubstituted, or optionally substituted at any position with one or more of R¹⁴, —OR¹⁵, —SR¹⁵, —N(R¹⁴)₂, R¹⁴C(O)—, nitro, or halo.
 2. A compound according to claim 1, wherein Y represents a saccharide moiety, and the saccharide moiety has the following structure:

wherein: R¹⁶ represents H or a protecting group; R¹⁷ represents H or OR¹⁶; and R¹⁸ represents R¹⁵.
 3. A compound according to claim 2, wherein R¹⁸ represents an alkyl group or R¹⁶.
 4. A compound according to claim 3, wherein R¹⁸ represents an alkyl group selected from the group consisting of methyl and ethyl.
 5. A compound according to claim 2, wherein R¹⁸ represents R¹⁶.
 6. A compound according to claim 1, wherein R represents:


7. A compound according to claim 6, wherein no more than one of R¹⁰, R¹¹, R¹², and R¹³ represent N.
 8. A compound according to claim 7, wherein R⁸, R⁹, and R¹³ represent N.
 9. A compound according to claim 1, wherein: R¹ represents CH; R² represents N; X represents H; and Y represents a saccharide moiety.
 10. A compound according to claim 9, wherein the saccharide moiety is a 1-ribosyl or 2-deoxy-1-ribosyl.
 11. A compound according to claim 1, wherein R represents:

R⁸ and R⁹ represent N; and R¹⁰, R¹¹, R¹², and R¹³ represent CH.
 12. A compound according to claim 1, wherein

R represents: R¹ represents CH; R², R⁸, and R⁹ represent N; R¹¹, R¹², and R¹³ represent CQ; Q and X represent H; and Y represents a saccharide moiety, wherein the saccharide moiety has the following structure:

wherein: R¹⁶ represents H or a protecting group; R¹⁷ represents H or OR¹⁶; and R¹⁸ represents R¹⁵.
 13. A compound according to claim 12, wherein R¹⁸ is represented by R¹⁶.
 14. A compound according to claim 12, wherein R¹⁸ is represented by an alkyl group, wherein the alkyl group is methyl or ethyl.
 15. A compound having the formula ZOR, wherein: Z represents:

R represents:

R¹ and R² independently represent CR³ or N; R⁴, R⁵, R⁶, R⁷, R⁸, R⁹, R¹⁰, R¹¹, R¹², and R¹³ represent, independently, N or CQ, with the proviso that no more than three of R⁴, R⁵, R⁶, R⁷ represents N; X represents R¹⁴, —OR¹⁵, SR¹⁵, —N(R¹⁴)₂, R¹⁴C(O)—, nitro, or halo; Q and R³, independently of each other, and independently at each position, represent R¹⁴, —OR¹⁵, —SR¹⁵, —N(R¹⁴)₂, R¹⁴C(O)—, nitro, or halo; Y represents a saccharide moiety having the following structure:

R¹⁴ independently represents H, an alkyl group, a carbocyclic aryl group, or a heterocyclic aryl group; R¹⁵ independently represents R¹⁴ or a protecting group;

R¹⁷ is hydrogen; and R¹⁸ is a protecting group; wherein: alkyl groups are branched or unbranched and have 1-18 carbon atoms; alkyl groups are optionally substituted with halo groups; carbocyclic aryl groups have a total of 6-20 carbon atoms, including carbon atoms of substituents; heterocyclic aryl groups have a total of 5-20 carbon atoms, including carbon atoms of substituents; and carbocyclic aryl groups and heterocyclic aryl groups are unsubstituted, or optionally substituted with one or more of R¹⁴, —OR¹⁵, —SR¹⁵, —N(R¹⁴)₂, R¹⁴C(O)—, nitro, or halo.
 16. A compound having the formula Z—O—R-(L)_(n)-Po, wherein: Z represents:

R represents:

R¹ and R² independently represent CR³ or N; R⁴, R⁵, R⁶, R⁷, R⁸, R⁹, R¹⁰, R¹¹, R¹², and R¹³ represent, independently, N or CQ, with the proviso that no more than three of R⁴, R⁵, R⁶, R⁷ represents N; X represents R¹⁴, —OR¹⁵, SR¹⁵, —N(R¹⁴)₂, R¹⁴C(O)—, nitro, or halo; Q and R³, independently of each other, and independently at each position, represent R¹⁴, —OR¹⁵, —SR¹⁵, —N(R¹⁴)₂, R¹⁴C(O)—, nitro, or halo; Y represents R¹⁴ or a saccharide moiety; R¹⁴ independently represents H, an alkyl group, a carbocyclic aryl group, or a heterocyclic aryl group; R¹⁵ independently represents R¹⁴ or a protecting group; wherein: alkyl groups are branched or unbranched and have 1-18 carbon atoms; alkyl groups are optionally substituted with halo groups; carbocyclic aryl groups have a total of 6-20 carbon atoms, including carbon atoms of substituents; heterocyclic aryl groups have a total of 5-20 carbon atoms, including carbon atoms of substituents; carbocyclic aryl groups and heterocyclic aryl groups are unsubstituted, or optionally substituted with one or more of R¹⁴, —OR¹⁵, —SR¹⁵, —N(R¹⁴)₂, R¹⁴C(O)—, nitro, or halo; L represents any chain of up to 20 atoms selected from the group consisting of carbon, nitrogen, oxygen, and sulfur moieties wherein: the carbon moiety is —CH₂—, —C(O)—, or phenyl; the nitrogen moiety is —N(R¹⁴)—, the oxygen moiety is —O—, the sulfur moiety is —S(O₂)—; with the proviso that when there is more than one oxygen moiety, at least two —CH₂— moieties are between the oxygen moieties; when there is more than one sulfur moiety, at least two —CH₂— moieties are between the sulfur moieties; where there is more than one —C(O)— moiety, at least one —CH₂— moiety is between the —C(O)— moieties; and not more than two nitrogen moieties are consecutive; n is 0 or 1; and Po represents an organic polymer, an inorganic polymer, or combinations thereof.
 17. The compound according to claim 16 wherein L is represented by -(A¹)_(a)-(A²)_(b)-(A³)_(c)-(Ph)_(k)-, wherein: A¹, A², and A³ independently represent —CH₂—, —C(O)—, —O—, —N(R¹⁴)—, or —S(O₂)—; each A¹, A², and A³ is different from the other two; Ph represents phenyl; a, b, and c are independently 0, 1, or 2; and k is 0 or
 1. 18. The compound according to claim 17 wherein at least one of a, b, and c is not
 0. 19. The compound according to claim 16 wherein L is represented by -(A¹-A²)_(m1)-(CH₂)_(m2)-(Ph)_(k)-Po, wherein: A¹ and A² independently represent —C(O)—, —O—, —N(R¹⁴)—, or —S(O₂)—; each A¹ and A² is different from the other; Ph represents phenyl; m1 and k are independently 0 or 1; and m2 is 0, 1, or
 2. 20. The compound according to claim 19 wherein at least one of m1 and m2 is not
 0. 21. The compound according to claim 16 wherein the organic polymer is polyethylene glycol, polystyrene, or an amino resin.
 22. The compound according to claim 16 wherein the inorganic polymer is glass beads, silica gel, alumina, controlled pore glass, or an amino-modified controlled pore glass.
 23. A compound according to claim 16, having the following structure: 